I have no objection to Titus being identified with the Beast, but I have not seen how the number 666 is to be "calculated" to indicate him.Scripture shows the Antichrist attacking and capturing Jerusalem and the Temple (Dan. 9:26; 11:36-12:13; Matt. 24:1-2, 15-21; 2 Thess. 2:4; Rev. 17-18). This was accomplished by Titus not Nero."
What I find perplexing is how any of the above scripture references could be said to identify the antichrist as the one who destroyed the temple [Titus].
In Daniel 9:26, those who destroy the temple are "the people" of the coming prince (my guess is that the "prince to come" in that passages is the "Prince of Rome"—just as the next chapter speaks of the Prince of Persia and the Prince of Grecia. These are apparently not human beings, but demonic entities associated with the rise and fall of successive empires). In any case, Daniel 9 says nothing of an antichrist, nor of any particular person (but rather "people") destroying the temple.
I agree that Daniel 11:36ff is probably about the Romans, and that the destruction of the temple is in view. However, I don't see any particular ruler, in this passage, being credited with that demolition, nor being identified as the Beast of Revelation.
Matthew 24 does not mention the antichrist, nor the Beast, at all, and does not attribute the predicted fall of the temple to the doing of any particular man.
2 Thessalonians 2 does not mention the destruction of the temple. The man of lawlessness (who may or may not be identified with Revelation's "Beast") sits in "the temple of God" (a term Paul uses, elsewhere, exclusively for the church), but its destruction is not predicted in the passage, and therefore is not attributed to the antichrist.
Revelation 17 does describe the destruction of the harlot Babylon (whom I identify as, probably, Jerusalem), but this destruction is not attributed to the Beast, nor to any man. The woman is apparently destroyed by the hostility of ten kings, who have previously been allied with the Beast (17:16). Nothing specifically would encourage the identification of Titus with the Beast here.
Again, I find this series of references perplexing, given the point they are alleged to prove. None of these passages (and no others that I know of) tell us about the Beast being the one who destroyed Jerusalem. Therefore, if this point is the whole case for making Titus out to be John's "Beast," it would seem to be a non-point. I would still be open to hearing the argument making the number 666 apply to Titus, however.