[skp]

I don't think that you should at all be worried when you put a raise in on the turn and no one makes it 3 bets. It's a near cinch that you have the best hand when the board does not pair on the river. When you have a King high flush, it's usually more comforting to have two opponents rather than one as one of them will be drawing to the nut flush (which means that the othetr does not have the nut flush).

I had a hand in a live 50-100 game on Saturday when this principle came into play.

I had raised UTG with KcQs. A very good player in MP 3 bet. Both players in the blinds called. I called.

Flop: Jc9c7c

VGP bets and we all call.

Turn: Ts

I bet. VGP raises in tempo. sb coldcalls and the bb folds.

The sb's coldcall made it clear to me that VGP was either on 88 or was trying the old raise the turn and check the river play with a hand he felt might be best but vulnerable (like a set). I thought this because I put the sb on the Ace of clubs draw which means that VGP could not have a flush given that he has neither the Ac or the Kc and he had 3 bet me preflop. So, I had an easy 3 bet on the turn. They both called.

I bet the river and the VGP made a good laydown (he later told me that he had a set and I believe him). The sb called me with presumably some kind of pair. He showed only the Ac after I tabled my hand.

Getting back to the river play on your hand:

I think that you have an easy bet on the river. You got a little lucky in that the player behind you bet. He could easily have been on a draw to the nut flush and simply checked the river costing you a call or two on the river.
The sb checkraises the dude and says he has a set. But what he says makes no difference. You almost surely have the best hand. If you are convinced that the limper will overcall, you should just call (because there is a slight chance that the sb may have you beat). But I don't think that you can be sure that the limper will overcall. Conversely, the limper may call even if you 3 bet if he has a lower flush which he could have. I would 3 bet.