Straight flush, what to do?

[Freyr]

8-handed 2/5 live game ($200 buy-in).

I've got $750 behind me, opponent has around $1100.

UTG calls, I limp in (UTG+2) with A[img]/images/graemlins/spade.gif[/img]7[img]/images/graemlins/spade.gif[/img];
button and bb call.

Flop: 8[img]/images/graemlins/spade.gif[/img]9[img]/images/graemlins/spade.gif[/img]10[img]/images/graemlins/spade.gif[/img]

Checked to me, I bet $20. BTN calls, BB raises to $60, I call while all others fold.

Turn: J [img]/images/graemlins/spade.gif[/img]

BB bets $120. I hesitate for a while, ask for time. Actually, my mind is spinning from the fact that I hit my first straight flush. Eventually I call.

River: 3 [img]/images/graemlins/club.gif[/img]

BB bets $350. The warning signals start to go off in my head. Laying down my first straight flush would be tough, but can I put him on anything other than the Q [img]/images/graemlins/spade.gif[/img]? Next he flashes a hole card, the 2 [img]/images/graemlins/club.gif[/img], and grins. He's acting like he obviously wants a call. But is he just acting?