I do know Him, personally, and Christ through Him, personally and have known Him for nigh onto a half century - not as concepts, but as Persons.
Evidently you cannot receive this, nevertheless to those who also know Him I testify that the indwelling Spirit (John 15-17, Romans 8, I Cor 2) authenticates both Peters testimony and Pauls epistles:
The Institute for Biblical & Scientific Studies does not mention any change to the Masoretic Text needed with reference to Deuteronomy 32:1-4. However, although we do have a non-MT Hebrew version of Deutoronomy 32 from cave 4, 4QDt(q) it only contains lines 37-43. So we cannot read anything into an omission here in comparing DSS to LXX.
But as to the faithfulness of the Torah itself there is no question. As I have already testified, the indwelling Spirit authenticates Scripture and leads us into Truth. (John 14, 15):
It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, [they] are spirit, and [they] are life. John 6:63
There were three different tasks of copying the OT. The Sopherim wrote the consonantal text. The Nakdanim added the vowel points and accents. The Masoretes added the marginal notes. An example is the Kethib (what is written) and Qere (what should be read). There are over 1,300 of these. The vowels of the Qere were written in the text of the Kethib. There are three different systems of vowel pointing, the Babylonian, Palestinian and Tiberian which the Masoretes created. The marginal notes called Masora were mainly written in Aramaic and were like a concordance.
Before the discovery of the Dead Sea Scrolls the Nash Papyrus was the oldest known witness to the OT which dated to the first or second century AD. It contained the decalogue. The second oldest were the Cairo Geniza fragments (about 200,000) which date to the fifth century AD (See Princeton Geniza Project). Most of these are in the Cambridge University Library and the Bodleian Library at Oxford. Today the oldest known text of the OT was discovered in 1979 in tombs across the Hinnom valley from Jerusalem. The text is the benediction of Aaron (Numbers 6:24-26) written on a silver amulet from the 7th century BC (Hoerth 1998, 386).
The oldest surviving manuscript of the complete Bible is the Codex Leningradensis which dates to 1008 AD. A Facsimile edition of this great codex is now available (Leningrad Codex 1998, Eerdmans for $225). The BHS (Biblia Hebraica Stuttgartensia) follows this codex. The most comprehensive collection of old Hebrew manuscripts is in the Russian Public Library in St. Petersburg formerly called Leningrad. Another important text is the Aleppo Codex which is now in Jerusalem. The HUB (Hebrew University Bible) follows the Aleppo Codex. The Isaiah and Jeremiah editions are now available. For a more detailed study see The Text of the Old Testament by Ernst Wurthwein and Textual Criticism: Recovering the Text of the Hebrew Bible by P. Kyle McCarter, Jr.
Nevertheless, the Jews always understood their responsibility to keep the Torah:
Ancient Hebrew Translation Project - wrt the translation of poetic form v mechanical v literal
Amen. This is either true, or Scripture is false.
We can debate the genuineness of someone's knowledge, whether or not it is truly of the Holy Spirit, but we can never disallow that this is the means by which the Holy Spirit moves throughout Scripture, throughout our lives and throughout history.
Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God: And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world. Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world. They are of the world: therefore speak they of the world, and the world heareth them. We are of God: he that knoweth God heareth us; he that is not of God heareth not us. Hereby know we the spirit of truth, and the spirit of error." -- 1 John 4:1-6"Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.