In Servants of God, the trainer is the main character from TRPG2.
Baz says that he's a veteran from the Shadow War, which narrows it down to one of your party members at the very least. Guy is out of the question, since he became a dean at the Academy, and I seriously doubt it's Gamblin' Jack. The trainer is also very skilled at psy, as well as stating that his parents died when he was young. That last one is practically a blazing neon sign, since, if memory serves, chapter 1 said something about his parents dying. (His parents are nowhere to be seen, at any rate, and he has to stay with his uncle)
- Final verdict as of the full game: It's never stated explicitly, but there are so many hints in favor that it seems pretty much a given.
Yahweh, like Nelis, is not an actual god, but an extremely powerful creature (or possibly spirit) and will be the final boss, fought in a similar way.
Think about it. Demanding worship, oppressive and prone to starting violence, called a god...where have we seen this before? It's basically Nelis' scheme, only with the humans and focused on being an actual religion. Since it apparently wants to kill off all psy users, there's probably a deeper plot around it, but this seems to be what the game is leading up to so far. (Plus, it's been heavily implied that we will be fighting D'Kah, and it isn't too much of a stretch to say that he'll be fought the way Tastidan was — you have to go through him to get to the final boss)
- The final boss part is Jossed at the very least — Craig has recently revealed that the final boss will be Cygnus. But then again, who's to say that Cygnus isn't Yahwah in the first place? He does wear that mask all the time...
- Final verdict as of the full game: Shrug of God. The nature of Yahweh is intentionally left ambiguous. Cygnus definitely isn't him, however, so the final boss part is explicitly Jossed.