I doubt that he has two pair given the board, obviously the straight is possible but I don't think that you're worried about that and neither am I (at least not without any info on player). If 2 pair is out of the question, then he probably has 77-TT (assuming any bigger pair would have raised prelop), a set or a big draw. Given that he would be scared by many turn cards if he has a mid-overpair, and if he has a draw hes not going anywhere, I'd say a push here is optimal.