PLO8 Dummy Straight, what should I have done on river?

Mistake 1--you bet the flop with that many people left to act behind you with nothing but a draw.

Mistake 2--I wouldn't have bet that river--he now has the same hand as you at worst (if he had a JK he probably has a king high straight now) then paying off the river. At those limits that raise on the river is almost always the nuts.

Oh btw--that flop hit someone--with that many hands somebody usually hits some crazy hand no matter how stupid it would have to be to have hit it.