What does villian think that you have? I'd say AA/KK/AK with a remote outside chance of QQ. Villian likely puts you on an overpair. Villian also (if he's any good) sense tremendous weakness from you now. Strong raise, 1/2 pot bet (giving villian 3:1 odds) and then a check on a flush/draw board. The all-in is a great chance to push you off your hand.

Villian called then called a big raise after someone else called the raise before him. That means low pp or a drawing hand, maybe SC? If he has a SC it's more likely he has two pair or a pair+OESD than a flush. Hands like QTd would play the same way. If I had two pair, I'd figure I'd had you beat, and so would villian.

Regardless of what you should have done (bet a little more on the flop and another pot size bet on the turn) you must call.