Party 10/20 Weak flush draw+gutshot in 4 way pot, Push, Call or Fold?

[IHateCats]

This was a hand from a little while ago that has been nagging me because I think I can make the case for several possible options here. I'm doing this from memory because Empire's HH have been funky for me lately.

Party 10/20 full ring
UTG+1 $3800 tight very aggro player opens for $70
MP1 $2200 NIT calls,
MP3 $1799 new player seems very loose, very passive calls,
Button (me) $2500 calls with 4s3s.
(It's a full table, everyone else folds.)

Flop is Js 6h 4s
Pot is about $300-330

UTG leads out for $200. Leading into 3 people with respectable stacks here I'm assuming he has overpair and my experience with him is that if it's AA, he'll go all the way with it no matter how obvious it might seem that he's beat.

MP1 calls the $200 as does MP3, making the pot over $1k. I HATE that MP3 calls since all I can reasonably put him on is a better flush draw but I don't know if he's a reasonable player and I'd guess that MP1 has a set here about 50% of the time and there is no way he's folding it for these size stacks no matter what I do. I can't see calling because unless a non spade 5 & especially if a spade comes and people keep betting I'm faced with the ugly decision of whether or not to fold because I doubt anyone folds a set with this kind of massive pot odds and will likely just push & I won't be able to tell difference between that and a higher flush which I have no outs to & pair plus flush draw is a possibility here. There's so much dead money, it's tempting to ignore all this potentially crap reasoning and push but if everyone calls and there is a set & higher flush draw, I'm basically dead meat drawing to 3 non spade 5's with massive ammounts of redraws against even that, but's it's a 1k pot and all my reasoning here is very speculative at best.

So what's the correct line here? Push, call or fold?