According to my calculations there should be $5 in the pot on the flop, which means you should bet about $4

when it comes back to you, here are your choices:

a) make a raise now, signaling great strength, because you are raising into a dry side pot after some one has called some one else's all in

b) flat-call, and then bet the turn, signaling great strength, because you are betting into a dry side pot after some one has called some one else's all in

b) has an advantage that there's a chance BB will lead the turn, but if he's strong enough to do that, he will probably call your flop raise (there's no reason for him to bluff a dry side pot)

which means you should go with a), because he has shown he likes his hand at least a little, and him seeing the turn card is much more likely to scare him than make him like his hand more (unless he's drawing with 34, in which case you don't want him to hit and like his hand more)

so the question is how much? I don't think it really matters. But if you don't raise all in, make sure to push the turn