[Nostrawho?]

at this point I would have to say that by your judgement of the BB, he was probably on a draw and felt priced in after your c/r, I would factor him out and take the check as a sign of a miss. I would put CO's bet on the flop as a standard play since he 3-bet pf with 2 cold players behind him, probably trying to assert a mid pair and isolate himself with you (which obviously didn't work). I'd say you have the best of it here and I think a bet is in order because there is no way CO wouldn't have raised on the turn if he were holding a premium pair or strong ace. I like a bet here, at worst a check call assuming BB is going to fold. Fold to a raise.