[Shaun]

Well, I'm not saying I'd do it, but I think to win this pot you need to bet about 1000$ here on the river. You cannot check, because he is likely to make a big bet you are going to have a hard time calling with no pair whether he has you beat or not. Is it possible that he has AQd or AKd? Maybe. He may also have some kind of pair/flush combo like you suggested. He might even have an overpair to the flop, something like tens, or even a set he is milking.

Of course if you just check you probably won't win the pot but won't lose anymore money either. Anyway, if your read is correct and he has a flush draw, pair or no pair I think you need to put him to a tough decision.