Some of these theories are mildly crazy.

Part of the Snarl? Really just doesn't make sense, at its basest. The Snarl is a being of divine strife and pure chaos that no one has heard of save a very select few.

The Tarrasque cannot reproduce.

Pit Fiend only has 1 quality that matches, total: the Wish.

KISS, guys. Occam's Razor, too. The farther you have to reach, the less chance it has of being true.