Checking flop is less for balance as our check-continuing range is essentially the same hand but without a 5 - i.e. AA+nfd or 789+fd or thereabouts - and more about inducing semibluffs from hands that might otherwise fold to a c-bet, and pot-control when we're behind which we are more often on a paired board where the cards are next to each other.
With this thinking do we put him on 5 6 then? I suppose if we were heads up we could but 3 handed it kinda means the other guy has called off 2k with a straight on a paired board. Stinker of a spot. If his watch is really nice we could call. Where's Lil D?
We're not putting one opponent on squarely one hand. What we need to remember is that due to card removal there is one 5 and three
left in the deck, and two opponents laying claim to some of these cards. What that means is we'll see one guy on 5x and the other on 66, the obvious nightmare scenario where we're dead to running kickers, much more often than we're comfortable with and is a large part of the reason to play for pot control in situations like this. The river is a fairly standard, easy fold, barring good->strong reads on both your opponents.