Where in the word of God, the Holy Bible, does it say the coming man of sin (the false messiah/the antichrist) he must be a Jew?
In Matthew 24:23-26 according to Jesus. The KJV phrase "false Christs" is the Greek word
pseudochristos, made up of 2 Greek words,
pseudo meaning false, and
christos meaning The Christ. Dr. James Strong in his Strong's Exhaustive Concordance translated
pseudochristos as 'a spurious Messiah' (Strong's no. 5580). That is about a false one who tries to exalt himself in place of The Messiah. And the Old Testament prophets foretold of Messiah (Isaiah 11; Deut.18:18; Psalms 72; Micah 5:2; Psalms 2; Jeremiah 23:5-6; etc.). Messiah, i.e., Jesus Christ, is the literal Son of David, His lineage having come from David's son Nathan (via Mary in Luke 3).
Also scripture is not talking about a literal temple being built but the temple of the body. It means that when the antichrist is revealed, he will be in the minds of men and women around the world be believed to be the messiah, to be God.
Sorry, but you've been misled. A stone temple in Jerusalem is exactly what Apostle Paul was pointing to in 2 Thess.2:4 with the "man of sin" coming there to sit in it and exalt himself in place of God. The main reason that is so is because a standing Jewish temple is required to fulfill the idol "abomination of desolation" prophecy that Jesus quoted from the Book of Daniel (see Daniel 11:31). Our LORD was good enough to give us a historical blueprint of what that "abomination of desolation" is with Antiochus Epiphanes IV who in 165 B.C. spiritually desolated inside the 2nd temple with an idol to Zeus, demanding all to bow to it.
And not only that I don't even think the self proclaiming Jews of the modern state of Israel are actual blood descendants. None of my research gives me any confidence they are. I will make a new post in this subforum about the "third temple" prophecy soon, please check it out.
I have no need to read your theory on that, because God's Word has already told us how to interpret those things.
And yes there are still literal bloodline Israelites of the house of Judah dwelling in the state of Israel today. In 1 Kings 11 God promised He would always leave one tribe in Jerusalem for David's and Jerusalem's sake, and He has done that throughout the centuries. There are many Jewish converts there too, but there are also bloodline descendants of Judah, Benjamin, Levi, and some small elements of the northern tribes, as was written about those who made up the southern kingdom of the "house of Judah" in God's Word, and regarding a small remnant of them that returned to Jerusalem from the Babylon captivity.
Edit: Though I do agree with you that the Pope is not the antichrist. Scripture tells us the man of sin will have a "coming". The world will know when he aims revealed (a revealing).
The 2 Thess.2 idea of his being revealed works differently between those in Christ and the deceived. For those in Christ, we are to know that false one will NOT be The True Christ. Thus Antichrist's arrival signals his being 'revealed' to us. But to the deceived who will believe Antichrist truly is God having come, he won't be 'revealed' to them until our Lord Jesus returns, and then they will recognize they have worshiped a fake in His place, and will then wish for the hills and mountains to fall upon them due to their shame. All this follows the warning parables The LORD gave through His prophets and by our Lord Jesus via witness of His Apostles.