I'd be folding this pre flop as it's not going to play well OOP. Post flop looks like an easy fold too, good chance we'll be up against a better flush.

I think calling J9s here is fine. You only need 22.22% realized eq to call. Against, a standard MP opening range and CO cold call range you have slightly above 27% eq. Hard to put an exact number on it, but I would say a suited gapper like this would realize at 100%, but maybe against 2 opponents and out of position only at 90%, which still gives you the eq you need to call.

Postflop: I think its a pretty easy fold. There just doesn't seem to be that much stuff that CO can be raising here, on this board, from his cold call range. Basically just sets and FDs. Can't see him raising with an over pair as he only has 99-JJ, maybe QQ, as over pairs, unless he slow played KK+. Most likely, he doesn't have any 2pair or SDs either and pretty much any FDs that he would be semi bluff raising with are bigger FDs than yours. That doesn't even take into account that you have MP, left to act behind you, who just bet into both of you. Would be pretty gross to call the CO raise and have MP jam.