Flop raise might actually take down the pot here, as villian is more likely to put you on spades than 2pair if you raise that flop after it was 3bet preflop. I guess you aren't getting any high spade in the hole to fold. I still think repping a hand like QsJs, 7s8s, 8s9s, isn't the worst thing you could do.

Do you guys like a lead when the 4th spade hits? You're guaranteeing a fold if villian is not holding a spade.