River bet for value against aggressive steal

[Tom Martell]

BB is 40/0 fish, and villain is 30/20. He's also aggressive post flop.

Party Poker 3/6 Hold'em (9 handed) converter

Preflop: Hero is SB with J[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/club.gif[/img].
UTG calls, <font color="#666666">5 folds</font>, <font color="#CC3333">Button villain raises</font>, <font color="#CC3333">Hero 3-bets</font>, BB calls, UTG folds, Button villain calls.

Wasn't sure what range of hands to place him on, as this could be a steal with any 2.

Flop: (10 SB) 7[img]/images/graemlins/heart.gif[/img], J[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, BB calls, <font color="#CC3333">villain raises</font>, <font color="#CC3333">Hero 3-bets</font>, BB folds, <font color="#CC3333">villain caps</font>, Hero calls.

Now I'm obviously worried about 77, but he'd play any A, especially AK or AQ, like this as well.

Turn: (9.50 BB) 3[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">villain raises</font>, Hero calls.

Getting scared off by the potential of his set, but not sold on it.

River: (13.50 BB) 8[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">villain raises</font>, Hero calls.

Is this hand strong enough against his range of holdings to value bet this river, or am I most likely up against a set here?

Final Pot: 17.50 BB