77 on a 754,8,x board, when do you stop raising and start calling?

[guvnorg]

Pokerstars, $3 $6

Raised pre flop and I call in mid position with 77. Flop top set 777 on a 754 board with 2 flush out, 5 handed.

Bet, call, raise, and re-raise infront of me and I cap, 4 to the turn as initial bettor folds.

Pot is gigantic already for these stakes.

Turn is 8 for a 8754 board, and it gets checked then bet to me. I hate raising here as it seems a 6 is such a big part of their range and I'm liable to get re-raised. I call and we go to the river 3 handed.

River is a K with no possible flush. First player checks, next guy bets. Do I raise here or just call? Should I be raising the turn?

Will post results later if any interest.