villain has limped 3 times until now and also their stack size being about 65bb makes me to think that it is safe to assume that villain is a fish.

Do you think that they would call 99-77 here? What if our opponent was a tag? Would he call those here?

I think that's a good card to bluff. When I assigned ranges for villain here, at this river they dont defend enough. They have a lot of missed fds, sds which fold. But most of those are beat from our King High.

I assumed that here they fold 99-77(which I think a fish calls on the turn, in addition to any 6.) and pairs of 6 and also 5s which had a fd as well on the turn. Also the J gives them trips but reduces those combos of J. I think it's good to bluff here.