In my opinion it was a very nice fold, to me he was surely in a flush draw, but for most fishes on these stakes the guy can be bluffing, that's why it's somehow a bluffable spot. But usually, when flop 2 suited cards and the guy bet and raises you and do all the stuff, it's very likely he has a flush draw.
By the way, I think you've played the hand the best manner possible, I mean, you couldn't guess he had a flush draw, the only thing that could change is the flop, inwhich a bet could be profitable to win the pot right there, and the villain would probably call, and you would fire another bulltet on the turn and he would probably fold