definitely iso-raise preflop. as played, i think you should still go ahead and bet/call the turn. checking is bad because there are soooo many river cards that will cost you the pot or at least a ton of value. any 3,4,8,9, or diamond makes a 4-straight or 4-flush. there's tons of weaker hands you will get paid off by if you bet the turn, even if he does turn up with the flush also a decent % of the time.