I'd raise pre, but I'd probably check A9o and definitely check A8o so really it can't be that bad.
Flop call is fine. You don't block any stab hands and you have 6 outs against most of his value range.
River check raise seems a little aggressive. I don't think a player at 4/8 is going to show up very often in a limped pot with a hand worse than AT that limps pre, bets when checked to on 633, checks back the turn 9 and bet/calls the river A.
That's not to say checking is bad. You may just conclude that he doesn't have anything and slipping it to him in this spot may be the only way to get money from him. I'd be more apt to bet at this level (where it's much more likely someone has a hand like 86 and didn't bet the turn for some reason) and check in games with more aggressive, stab-happy opponents.