I think if you'er going to call the river bet after fourth street, just put him all in. You played it fine. Villian doesn't have that much more. If he was sitting on 800 you would be faced with a difficult problem. There are a lot of hands that people love to donkey bet the turn with,like top pair, flush draws, and other crazy fish hands. But the nut flush happens to be the best. Seems more unlucky than anything else.