100NL - Top set on 3 card straight flop, 4-way limped pot. Too weak?

[badatmath]

I didn't think SB would check such a drawy flop with 2 pair or a set in a 4-way pot. Was that a mistake? On the turn he makes a big bet, looking very straight-like to me now, but I can still fill up and maybe stack him. His river check seems weak since I called a big bet on the turn and probably didn't look like I was drawing, but I just didn't think he'd play the flop like that without a straight so I didn't value bet. Looking back I think I should have bet the river and folded to a raise. Do you agree? Do you think the flop and turn were too weak too? I also think I bet too small on the flop and I'm trying to stop doing that.

Thanks, Matt

PokerStars No-Limit Hold'em, $1.00 BB (8 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

CO ($110)
Button ($151.35)
SB ($96.80)
BB ($140.20)
UTG ($44.35)
UTG+1 ($104.75)
MP1 ($104.15)
Hero ($64)

Preflop: Hero is MP2 with 4[img]/images/graemlins/club.gif[/img], 4[img]/images/graemlins/spade.gif[/img].
UTG calls $1, <font color="#666666">2 folds</font>, Hero calls $1, <font color="#666666">2 folds</font>, SB completes, BB checks.

Flop: ($4) 3[img]/images/graemlins/spade.gif[/img], 2[img]/images/graemlins/club.gif[/img], 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, BB checks, UTG checks, <font color="#CC3333">Hero bets $2</font>, <font color="#CC3333">SB raises to $6</font>, BB folds, UTG folds, Hero calls $4.

Turn: ($16) 8[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $13</font>, Hero calls $13.

River: ($42) 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, Hero checks.

Final Pot: $42