I’m never folding here in this structure. Direct odds are 3:1, so you’re not quite getting the right price to call for your flush, but with the guy behind probably adding money to the pot you are getting a good price to call. If you didn’t have the nut flush draw that would be different, but since you do yo have to call.
Why did you think BB was going to raise? He hasn’t shown any aggression in the hand, so unless he’s got some weird 2 pair I don’t see what he’s raising with.
That structure must be tough to play. I live in AZ, but at least our spread limit for 3/5 is a $500 max bet. You probably need to read up on some limit theory, since I imagine a lot of turns and rivers play more like a limit game.