That's an interesting theory that Sam is taking on other people's powers rather than having telekinesis himself, but what about his visions? Speaking of which, while it makes perfect sense for the final crash to be a Sam!Vision, I sure would feel played and disappointed if that's the way the writers choose to go.

I think that Sam is probably possessed (somewhat) by the demon too, but I'm not sure I'm following the "Mary and Jess were in the way" theory. From what John said in Salvation, in all the families that the demon has gone after, all the victims were the mother of the baby. They can't all be in the way (instead of, say, the father)??