well, he called PSB on the flop so obviously he has something, whether he's "slowplaying" or has a draw, its something. I think I would bet like 6 on the flop and def. slow down if he calls it. as played I think you def. check the turn, probably call up to a PSB and check/ re-evauluate river. If it goes check-check you can value bet the river depending on the card, i.e. draws brick off.
as played, that is a nasty river card, and if it was the deuce of hearts or some other brick, I'd say you should value shove the river, because if he had 2 pair or a set on the turn, not raising is criminal, but everything except the flush just got there, KQ, QJ, KJ, str8, all of which he is probably not folding. i'd check and hope it goes check/check but i think you definatley gotta muck it on this river if he makes any kinda decent bet. i guess if you had some kinda read that he could laydown a hand you could open shove river, knowing its a bluff, but this is generally bad with no read at a 50 NL table.