Flopped a straight, now what (and when to raise/cap the river)?

Multitabling, no good reads. I don't remember what he was then but here's my current stats on the SB:
20.61/5.45/1.52 (165 hands)

Party Poker 0.50/1 Hold'em (10 handed) converter

Preflop: Hero is MP2 with K[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/club.gif[/img].
<font color="#666666">4 folds</font>, <font color="#CC3333">Hero raises</font>, <font color="#666666">3 folds</font>, SB calls, BB calls.

Flop: (6 SB) J[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/club.gif[/img], T[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, BB checks, Hero checks.

Ok, I think this calls for a slow play? Though I was the raiser so maybe I should have bet out.

Turn: (3 BB) 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">SB bets</font>, BB folds, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">SB 3-bets</font>, <font color="#CC3333">Hero caps</font>, SB calls.

I still have the nuts, though if the board pairs or a flush comes out I might have a problem.

River: (11 BB) A[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets</font>, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">SB 3-bets</font>, Hero calls.

I think it's +EV to raise here, if I am raised and lose more than 1/3 of the time it isn't but if I win more than 2/3's of the time I will have +EV (assuming the raise is called, which I think it will be). I still beat a lot of stong hands. Am I strong enough to cap? Then I only have to win more than 1/2 of the time to show a profit (against a stronger set of hands).