4-Card PLO50 AK66ds probing turn and facing river bet in 3BP oop

Pre and flop standard. Turn is probably fine to bet as protection and thin value. Problem is of course river visibility.

River seems like standard x-c to me. We beat bluffs so I don't like to use this as x-r bluff. Not that I would often try to bluff x-r anyway as opponent is getting very good pot odds. Problem is villain could perhaps value bet some Kx two pair but we do block K. I think lot of people would downsize if value betting two pair.

In general if we choose to bluff in river spot like this we want to unblock bottom of villain potential value range. In this view K is bad to have. Though it does also block KK but that would likely raise turn.

Other nice thing for river x-c is unblocking QJT and spade. In a way 66 is also better than 77 as now it's more easy for villain to have e.g. T7 to bluff with. Question though is how much is villain checking flop with stronger straight draws? Lot of wraps would probably bet but most likely combo to check is 76 which could also include some of weakest wraps. So seemingly there are lot of busted draws but villain flop check could cut away lot of those in reality.

Thanks for input. Yeah, river check-call came into my mind aswell, I think it's still close between X/F and X/C but since he is loose I could X/C. I dont like X/R for the reasons you mentioned.