NL2: Bottom set facing minraise and river bet on scaryish board

[stillnaive]

Villain is running 24/3/.9 over a limited hand history, about 50 hands. I have been running over the table after I slowrolled a flopped nut straight about thirty hands prior and stacked two people; I couldn't get anyone to call a preflop bet of over 3x, so I had loosened up my starting requirements a bit to steal more against the passive table. I believe I took down 15 of the 30 hands, most of them preflop or on a continuation bet.

Villain isn't aggressive postflop at all, and I've been mercilessly stealing from him. He could be playing back, but it's hard to say; he would limp KQ, from what I've seen. The only time I've seen him raise preflop, he was holding QQ+. Are you folding to the possibility of a higher set or the straight?

PokerStars No-Limit Hold'em, $0.02 BB (3 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Hero ($3.38)
Button ($2.53)
SB ($0.77)

Preflop: Hero is BB with 4[img]/images/graemlins/club.gif[/img], 4[img]/images/graemlins/heart.gif[/img].
Button calls $0.02, SB completes, Hero checks.

Flop: ($0.06) A[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/diamond.gif[/img], J[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, <font color="#CC3333">Hero bets $0.06</font>, Button calls $0.06, SB folds.

Turn: ($0.18) T[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $0.18</font>, <font color="#CC3333">Button raises to $0.36</font>, Hero calls $0.18.

River: ($0.90) 6[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">Button bets $0.2</font>, <font color="#CC3333">Hero puts it in but isn't surprised if he loses? Or should he just call? (I assume he can't fold, can he?)