There is no way he has 77 here, you would have stacked him with that. He is worried about you having a 4 for trips. I am guessing he has an overpair or A7. A spade may kill any action on the river, but I doubt it. I believe he has $233 of his stack in a pot of $490 and about $160 left....call his raise on the turn and hopefully he bets into you on the river....if not push.