I think this was a very well reasoned argument. I would just differ on a couple of small details.
1. He had to be crucified on Passover. One day before wasn't close enough for him to be "our passover is sacrificed for us" (1 Co 5:7)
2. Your article makes the supposition that the lambs were killed before Nisan 14, on the afternoon of Nisan 13.
Exo 12:6 And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening.
You stated that Jewish tradition said the lambs were killed at 3 PM on the 13th. This would seem to violate Gods command. It hinges on the word "evening". I believe if you do a study on this word, you'll find that it must pertain to the time period after the sunsets, or just after the sunsets, but surely not in the afternoon.
3. Is Passover a sabbath biblically?
Lev 23:5 In the fourteenth [day] of the first month at even [is] the LORD'S passover.
Notice that there is no injunction against working.
Lev 23:6 And on the fifteenth day of the same month [is] the feast of unleavened bread unto the LORD: seven days ye must eat unleavened bread.
Lev 23:7 In the first day ye shall have an holy convocation: ye shall do no servile work therein.
These verses are linked. Unleavened bread begins the 15th and being the first day of unleavened bread, it's a sabbath, a day of rest.
Lev 23:8 But ye shall offer an offering made by fire unto the LORD seven days: in the seventh day [is] an holy convocation: ye shall do no servile work [therein].
As is the last day.
So how does this fit in? Jesus had his passover meal with the disciples on Tuesday night, just after sunset, the time when the lambs would have been slain. He instituted two new ordinances and TOLD us that the bread represents his body, and the wine his shed blood. He did this at the same time the lambs were to be killed.
He died on passover at around 3 pm Wednesday and had to be buried before the sabbath of the first day of unleavened bread started because it wasn't legal to bury corpses on the sabbath. He was entombed just before sunset.
As you said, he HAD to be in the grave 3 days and 3 nights or else he was not the messiah. It was the only sign that told us that he would be:
Mat 12:39 But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas:
Mat 12:40 For as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth.
Anyways, I think these are relatively minor points and I congratulate you on proving the truth for yourself.
That's the only verse (besides the Jonah reference) mentioning "three days and three nights", in the context of what might be a metaphor for a grave, but it says "son of man", not "I" or "Jesus". Now we know that he did refer to Himself with that phrase, but can we safely assume that was always the case? After all, Ezekiel was addressed as "son of man" many times, Daniel once. There could be others but those are the only two I have found. Plus there is this tidbit regarding two prophets:
Revelation 11:7-12
7 And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them.
8 And their dead bodies shall lie in the street of the great city, which spiritually is called Sodom and Egypt, where also our Lord was crucified.
9 And they of the people and kindreds and tongues and nations shall see their dead bodies three days and an half, and shall not suffer their dead bodies to be put in graves.
10 And they that dwell upon the earth shall rejoice over them, and make merry, and shall send gifts one to another; because these two prophets tormented them that dwelt on the earth.
11 And after three days and an half the Spirit of life from God entered into them, and they stood upon their feet; and great fear fell upon them which saw them.
12 And they heard a great voice from heaven saying unto them, Come up hither. And they ascended up to heaven in a cloud; and their enemies beheld them.
Mat 12:39 But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas:
Mat 12:40 For as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth.
heart of the earth
Matthew 6:19-24
19 Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and where thieves break through and steal:
20 But lay up for yourselves treasures in heaven, where neither moth nor rust doth corrupt, and where thieves do not break through nor steal:
21 For where your treasure is, there will your heart be also.
22 The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light.
23 But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great is that darkness!
24 No man can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. Ye cannot serve God and mammon.
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Matthew 24:27 For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be.
Matthew 24:28 For wheresoever the carcase is, there will the eagles be gathered together.