I would fold. One of the key factors is 5 people seeing the flop. It is not worth risking your stack in a marginal situation such as this. Remember, it is not another $100 to call as he will likely pressure you the rest of the hand and eventually make you decide for your whole stack.

If you are pretty sure the button will CB this flop, I would actually check the flop to him and C/R him. This will provide a couple of things. First of all, if you are C/R, than you will likely know where you are at far better once he does his action. He may fold and if he calls or raises, you know you are beat and can not put in another dime unless you improve. If he checks behind, you can play the rest of the hand in a weak mannor and try to get a cheap showdown.