Wow. A lot to read. (though I know most of it)
The Antichrist will only be able to take the seat in the temple of God in Jerusalem and declare himself God because a majority of the people have become antichrist.
Also, it is possible that the Antichrist will not be just one person, but a very tightknit group of say, 3 people. Just in what you quoted, there are at least TWO, the Dragon and the Beast. Isn’t there also a harlot?
One of them will be the Leader, as far as the public is concerned, so he could be labeled the Antichrist.
At any rate, the Antichrist (whether one person or several) will have the ‘power’ of all the humans who have become antichrist. I think that is what is being explained by the Dragon giving the Beast power. The Dragon controls the populace, and gives the power to the Beast (making the populace do whatever the Beast wants).
Basically, we agree, don’t you think?
“Isn’t there also a harlot?”
The harlot is not a person though, the harlot is a city (and perhaps by extension the things associated with that city):
“And the woman which thou sawest is that great city, which reigneth over the kings of the earth.” Rev. 17:18
Compare with Isaiah 1:21:
“How is the faithful city become an harlot! it was full of judgment; righteousness lodged in it; but now murderers.”
This is speaking of, as it says at the beginning of the chapter, “concerning Judah and Jerusalem in the days of Uzziah, Jotham, Ahaz, and Hezekiah, kings of Judah.”
So the harlot there is Jerusalem, but perhaps by extension representing the people and kings of Judah.