Didn't the Pocket Dimension theory get tossed? If I am recalling correctly, the main evidence for it wasn't that Lavos is at the same power level whenever he was faced (since there isn't a significant passing of time between these instances) but rather that one can face the shell in one period, defeat it, then go back in time and not need to face it again (with the exception being during the Ocean Palace Incident). Given that it requires the party intentionally behave irrationally and that the Pocket Dimension theory doesn't even address all instances of its own evidence, it seemed like it had been rejected.
Anywho, that aside...
Lavos couldn't have wanted to be sent to the DBT because it would then be a threat to its own species (if it was able to become the TD) or it wouldn't have been assured it could become the TD (if it was able to send Schala there intentionally, and it wanted to become the TD, why not also send itself there?)
The Entity's role in the game is presented as very passive. The most active part it does is share its memories with the party: there is no indication that it wants them to destroy Lavos (it might not have thought about it). Rather, given the themes of the game, it seems most likely that the party themselves were the ones to take the initiative, not the Entity. Therefore, it seems unlikely that the entity would have even thought there was a need to protect the party.
Yes, but the theory can not be disproven, which makes it possible. There are a lot of contradicting points, but none concrete enough to discard the theory.
If it can't be disproven, then it really isn't a theory to begin with but rather fanfiction.
Well, if we assume the theories in DBT and TB page are true, then if someone does a Time Travel, the original timeline will be DBT'd.
Or did I misunderstand?
Nope, that's correct. If TB is correct, Lavos doesn't even need to have himself killed to gain access to the DBT. Though, becoming a TD, he would also be threatening his own non-TD existence, since the two aren't mutually exclusive.