Flop middle set in a big pot. What's the play?

[flytrap]

Loose game at Greektown in Detroit. Blinds are 2-2-5, with 2 on the button. I have about $1200. I'm on the button with 55. In this game, if people call the first $5 they will call $35 or $40 more. 2 loosies call, a good, tight player with about $1100 makes it $35, two people call, I call, original limpers call. 6 to the flop with about $200 in the pot. Flop is A52 rainbow. It checks around to me, I bet $70. Orinal preflop raiser makes it $170. I call. On the turn he bets $100. What's the play?