The Apostles considered it Scripture. They quote from it. They use is as Scriputre (OT). The number of verses where they quote verses different from those of the Pharisaical bible is astaunding, and so is the Protestant denial:
Be your own witness.
Matt. 1:23 / Isaiah 7:14 - behold, a "virgin" shall conceive. Hebrew - behold, a "young woman" shall conceive.
Matt. 3:3; Mark 1:3; John 1:23 / Isaiah 40:3 - make "His paths straight." Hebrew - make "level in the desert a highway."
Matt. 9:13; 12:7 / Hosea 6:6 - I desire "mercy" and not sacrifice. Hebrew - I desire "goodness" and not sacrifice.
Matt. 12:21 / Isaiah 42:4 - in His name will the Gentiles hope (or trust). Hebrew - the isles shall wait for his law.
Matt. 13:15 / Isaiah 6:10 - heart grown dull; eyes have closed; to heal. Hebrew - heart is fat; ears are heavy; eyes are shut; be healed.
Matt. 15:9; Mark 7:7 / Isaiah 29:13 - teaching as doctrines the precepts of men. Hebrew - a commandment of men (not doctrines).
Matt. 21:16 / Psalm 8:2 - out of the mouth of babes and sucklings thou has "perfect praise." Hebrew - thou has "established strength."
Mark 7:6-8 – Jesus quotes Isaiah 29:13 from the Septuagint – “This people honors me with their lips, but their heart is far from me; in vain do they worship me, teaching as doctrines the precepts of men.”
Luke 3:5-6 / Isaiah 40:4-5 - crooked be made straight, rough ways smooth, shall see salvation. Hebrew - omits these phrases.
Luke 4:18 / Isaiah 61:1 - and recovering of sight to the blind. Hebrew - the opening of prison to them that are bound.
Luke 4:18 / Isaiah 58:6 - to set at liberty those that are oppressed (or bruised). Hebrew - to let the oppressed go free.
John 6:31 / Psalm 78:24 - He gave them "bread" out of heaven to eat. Hebrew - gave them "food" or "grain" from heaven.
John 12:38 / Isaiah 53:1 - who has believed our "report?" Hebrew - who has believed our "message?"
John 12:40 / Isaiah 6:10 - lest they should see with eyes...turn for me to heal them. Hebrew - shut their eyes...and be healed.
Acts 2:19 / Joel 2:30 - blood and fire and "vapor" of smoke. Hebrew - blood and fire and "pillars" or "columns" of smoke.
Acts 2:25-26 / Psalm 16:8 - I saw...tongue rejoiced...dwell in hope.. Hebrew - I have set...glory rejoiced...dwell in safety.
Acts 4:26 / Psalm 2:1 - the rulers "were gathered together." Hebrew - rulers "take counsel together."
Acts 7:14 / Gen. 46:27; Deut. 10:22 - Stephen says "seventy-five" souls went down to Egypt. Hebrew - "seventy" people went.
Acts 7:27-28 / Exodus 2:14 - uses "ruler" and judge; killed the Egyptian "yesterday." Hebrew - uses "prince" and there is no reference to "yesterday."
Acts 7:43 / Amos 5:26-27 - the tent of "Moloch" and star of god of Rephan. Hebrew - "your king," shrine, and star of your god.
Acts 8:33 / Isaiah 53:7-8 - in his humiliation justice was denied him. Hebrew - by oppression...he was taken away.
Acts 13:41 / Habakkuk 1:5 - you "scoffers" and wonder and "perish." Hebrew - you "among the nations," and "be astounded."
Acts 15:17 / Amos 9:12 - the rest (or remnant) of "men." Hebrew - the remnant of "Edom."
Rom. 2:24 / Isaiah 52:5 - the name of God is blasphemed among the Gentiles. Hebrew - blasphemed (there is no mention of the Gentiles).
Rom. 3:4 / Psalm 51:4 - thou mayest "prevail" (or overcome) when thou art judged. Hebrew - thou might "be clear" when thou judges.
Rom. 3:12 / Psalm 14:1,3 - they "have gone wrong." Hebrew - they are "corrupt" or "filthy."
Rom. 3:13 / Psalm 5:9 - they use their tongues to deceive. Hebrew - they flatter with their tongues. There is no "deceit" language.
Rom. 3:13 / Psalm 140:3 - the venom of "asps" is under their lips. Hebrew - "Adder's" poison is under their lips.
Rom. 3:14 / Psalm 10:7 - whose mouth is full of curses and "bitterness." Hebrew - cursing and "deceit and oppression."
Rom. 9:17 / Exodus 9:16 - my power "in you"; my name may be "proclaimed." Hebrew - show "thee"; may name might be "declared."
Rom. 9:25 / Hosea 2:23 - I will call my people; I will call my beloved. Hebrew - I will have mercy (love versus mercy).
Rom. 9:27 / Isaiah 10:22 - only a remnant of them "will be saved." Hebrew - only a remnant of them "will return."
Rom. 9:29 / Isaiah 1:9 - had not left us "children." Hebrew - Jehova had left us a "very small remnant."
Rom. 9:33; 10:11; 1 Peter 2:6 / Isaiah 28:16 - he who believes will not be "put to shame." Hebrew - shall not be "in haste."
Rom. 10:18 / Psalm 19:4 - their "voice" has gone out. Hebrew - their "line" is gone out.
Rom. 10:20 / Isaiah 65:1 - I have "shown myself" to those who did not ask for me. Hebrew - I am "inquired of" by them.
Rom. 10:21 / Isaiah 65:2 - a "disobedient and contrary" people. Hebrew - a "rebellious" people.
Rom. 11:9-10 / Psalm 69:22-23 - "pitfall" and "retribution" and "bend their backs." Hebrew - "trap" and "make their loins shake."
Rom. 11:26 / Isaiah 59:20 - will banish "ungodliness." Hebrew - turn from "transgression."
Rom. 11:27 / Isaiah 27:9 - when I take away their sins. Hebrew - this is all the fruit of taking away his sin.
Rom. 11:34; 1 Cor. 2:16 / Isaiah 40:13 -the "mind" of the Lord; His "counselor." Hebrew - "spirit" of the Lord; "taught" Him.
Rom. 12:20 / Prov. 25:21 - feed him and give him to drink. Hebrew - give him "bread" to eat and "water" to drink.
Rom. 15:12 / Isaiah 11:10 - the root of Jesse..."to rule the Gentiles." Hebrew - stands for an ensign. There is nothing about the Gentiles.
Rom. 15:21 / Isaiah 52:15 - been told "of him"; heard "of him." Hebrew - does not mention "him" (the object of the prophecy).
1 Cor. 1:19 / Isaiah 29:14 - "I will destroy" the wisdom of the wise. Hebrew - wisdom of their wise men "shall perish."
1 Cor. 5:13 / Deut. 17:7 - remove the "wicked person." Hebrew - purge the "evil." This is more generic evil in the MT.
1 Cor. 15:55 / Hosea 13:14 - O death, where is thy "sting?" Hebrew - O death, where are your "plagues?"
2 Cor. 4:13 / Psalm 116:10 - I believed and so I spoke (past tense). Hebrew - I believe, for I will speak (future tense).
2 Cor. 6:2 / Isaiah 49:8 - I have "listened" to you. Hebrew - I have "answered" you.
Gal. 3:10 / Deut. 27:26 - cursed be every one who does not "abide" by all things. Hebrew - does not "confirm" the words.
Gal. 3:13 / Deut. 21:23 - cursed is everyone who hangs on a "tree." Hebrew - a hanged man is accursed. The word "tree" does not follow.
Gal. 4:27 / Isaiah 54:1 - "rejoice" and "break forth and shout." Hebrew - "sing" and "break forth into singing."
2 Tim. 2:19 / Num. 16:5 - The Lord "knows" those who are His. Hebrew - God will "show" who are His.
Heb. 1:6 / Deut. 32:43 - let all the angels of God worship Him. Hebrew - the Masoretic text omits this phrase from Deut. 32:43.
Heb. 1:12 / Psalm 102:25 - like a "mantle" ... "roll them"... "will be changed." Hebrew - "raiment"... "change"..."pass away."
Heb. 2:7 / Psalm 8:5 - thou has made Him a little "lower than angels." Hebrew - made Him but a little "lower than God."
Heb. 2:12 / Psalm 22:22 - I will " sing" thy praise. Hebrew - I will praise thee. The LXX and most NTs (but not the RSV) have "sing."
Heb. 2:13 / Isaiah 8:17 - I will "put my trust in Him." Hebrew - I will "look for Him."
Heb. 3:15 / Psalm 95:8 - do not harden your hearts as "in the rebellion." Hebrew - harden not your hearts "as at Meribah."
Heb. 3:15; 4:7 / Psalm 95:7 - when you hear His voice do not harden not your hearts. Hebrew - oh that you would hear His voice!
Heb. 8:9-10 / Jer. 31:32-33 - (nothing about husband); laws into their mind. Hebrew - I was a husband; law in their inward parts.
Heb. 9:28 / Isaiah 10:22 - "to save those" who are eagerly awaiting for Him. Hebrew - a remnant of them "shall return."
Heb. 10:5 / Psalm 40:6 - "but a body hast thou prepared for me." Hebrew - "mine ears hast thou opened."
Heb. 10:38 / Hab. 2:3-4 - if he shrinks (or draws) back, my soul shall have no pleasure. Hebrew - his soul is puffed up, not upright.
Heb. 11:5 / Gen. 5:24 - Enoch was not "found." Hebrew - Enoch was "not."
Heb. 11:21 / Gen. 47:31 - Israel, bowing "over the head of his staff." Hebrew - there is nothing about bowing over the head of his staff.
Heb. 12:6 / Prov. 3:12 - He chastises every son whom He receives. Hebrew - even as a father the son in whom he delights.
Heb. 13:6 / Psalm 118:6 - the Lord "is my helper." Hebrew - Jehova "is on my side." The LXX and the NT are identical.
James 4:6 / Prov. 3:34 - God opposes the proud but gives grace to the humble. Hebrew - He scoffs at scoffers and gives grace to the lowly.
1 Peter 1:24 / Isaiah 40:6 - all its "glory" like the flower. Hebrew - all the "goodliness" as the flower.
1 Pet. 2:9 / Exodus 19:6 - you are a "royal priesthood." Hebrew - you shall be to me a "kingdom of priests."
1 Pet. 2:9 / Isaiah 43:21 - God's own people...who called you out of darkness. Heb. - which I formed myself. These are different actions.
1 Pet. 2:22 / Isaiah 53:9 - he "committed no sin." Hebrew - he "had done no violence."
1 Pet. 4:18 / Prov. 11:31 - if a righteous man "is scarcely saved." Hebrew - if the righteous "is recompensed."
1 Pet. 5:5 / Prov. 3:34 - God opposes the proud but gives grace to the humble. Hebrew - He scoffs at scoffers and gives grace to lowly.
Isaiah 11:2 - this verse describes the Seven Gifts of the Holy Spirit, but the seventh gift, "piety," is only found in the Septuagint.
Ref http://www.scripturecatholic.com/septuagint.html
If any of these agree with the KJV or any current English Bible, that means you are reading Septuagint as Scriputre and not the Hebrew Bible. And I can tell you Matt. 1:23 / Isaiah 7:14 in YOUR Bible is from the Septuagint!
All we know for sure is that they approved of some of it, or maybe even the vast majority of it. Quoting several lines does not say that they believed the whole thing was inspired. I'm sure we could quote passages from Mormon writings with approval, but that doesn't mean we accept their texts as scripture. If they did accept all of it as scripture, then why did they not quote from it exclusively?
I read through your whole list and while there are clear differences, I did not see any major contradictions. The principles are still the same. I can read the NIV or the KJV (or others) and be fully confident in any of them.
And I can tell you Matt. 1:23 / Isaiah 7:14 in YOUR Bible is from the Septuagint!
No argument here. That's what it says. Here is the note in my Bible on Is. 7:14 :
God's sign to Ahaz was that of a virgin and her son, who would not be more than 12 to 14 years old before Syria and Israel would be captured in 722 B.C. (When the prophecy was spoken, it probably referred to the woman, a virgin at that time, who Isaiah took later as his second wife, 8:1-4, his first wife presumably having died after the birth of Shear-Jashub, 7:3.) The virgin of Isaiah's prophecy is a type of the virgin Mary, who, by the Holy Spirit, miraculously conceived Jesus Christ. See Matt 1:23. The Hebrew word here that is translated "virgin" is found elsewhere in the OT in Gen. 24:43, Ex. 2:8, Ps. 68:25, Prov. 30:19, Song 1:3, 6:8, and in those instances refers only to a chaste maiden who is unmarried.
Is there any way to know that for certain? How do we know that many or most of these were not taken from the New Testament and just inserted into the Septuagint during the New Testament period, or during some of the revisions of the Septuagint, rather than vice versa???
Are the readings here from the Septuagint of Codex B, or Sinaiticus, or Alexandrinus or some later revisions? Hasn't the Septuagint been under revision for 2000 years and no one is really sure just what the pre-Origen Septuagint really was???