Bottom set, turn completes straight

[rannerboy]

Live shorthanded tournament. My stack is ~7000, blinds 100/200.

I'm on the button and pick up 4 [img]/images/graemlins/club.gif[/img]4 [img]/images/graemlins/heart.gif[/img]. Two limpers to me, I limp, SB calls, BB checks.

Flop: 4 [img]/images/graemlins/spade.gif[/img]5 [img]/images/graemlins/diamond.gif[/img]7 [img]/images/graemlins/club.gif[/img] (Pot 1000)

Checked to me. I bet 700 (too small?). BB thinks for a while, then calls. Everyone else folds. BB is a rather loose, tricky player. He covers me.

Turn: 6 [img]/images/graemlins/heart.gif[/img] (Pot 2400)

Now that's a really scary card... He checks. I bet 1200. He calls. Was it correct to bet here? Bet size?

River: A [img]/images/graemlins/heart.gif[/img]

He thinks for quite a long time before he checks. I immediately check behind. Does anyone bet here? I was really satisfied to get a free showdown here.