Live 2/5 Hand - flopped 3rd nuts, tons of action

[TomCollins]

I have 77 in middle position. Table is fairly passive, one poor player on my left, fairly tight player in the blinds, and guy who just lost a huge pot on flopped set of Kings against a gutshot straight.

Stacks:
Tilter: 600ish
Me: 900ish
Fish: 300ish
Button: 300ish

Tilter limps, I limp, fish raises to 25, button calls 25, all 3 call.

Flop is 6c7cTd.

Tilter checks, I check, fish bets 25, button makes it 75. Tilter checkrasies all in for 535.

I???