First hand: he's an idiot with AJ or a decent player with 66. Either way I think that's a fold. Second hand: not sure. It's hard to imagine him re-re-raising with a hand that the 8 would help (i.e. a straight draw). He's either ahead of you already, or still behind you on the turn. I wonder if he had AJ or KJ. Might just put him all in on the turn.

edit: one thing I didn't notice is that he check-raised on that hand. I would put him on two pair (obviously the same two pair or a worse two pair) and get all his money in the pot.