[levAA]

First I think we should check the possible ranges of villains - specially of SB, who is more dangerous here i think.

I would set him on:
22-99,AT,AJ,AQ,KQ,KJ,QJ,JTs(?)

With: AJ,KJ,QJ,JT,33,77 he would consider a c/r - so as answer to your second question should be in 6/15 or 40%.

With: 88,99 he migh flat call your c-bet, as well as with something like KsQs.

So to answer your first question i would not c-bet here, but take the free-card a reorientate on the turn. maybe we get a possibility for a delayed c-bet here, maybe we draw one of our 2 out, or maybe things get just clearer.