Btn is a weak player 55 vpip. After the flop checks and the reg in the sb checks again I think we have to bet in this spot because the reg capped his range. When the weak player calls ott I think his range looks like one pairs hands, some sd that didnt cbet the flop, and some AK/AQ/AJ type of hands. Even if we block some of his folding range I think we have to bluff and fold hands like J9, A2,A7, you get the idea.