hand 1 I don't see the need to bluff second pair when we might be good a lot
I mean you say he opens K6s from UTG, so that means he has any suited king in his range here on the river, do you think he folds them?

hand 2 yeti theorem, be more obvious
if I'm raising like AT/JJ here your 3b makes no sense because you'd probably choose to slowplay a set on such a dry board (not that you would, but I still would assume that) so I'd stick it in
you also rep nothing but sets since the top of your range pf you will 3b

hand 3 I like your 3b, since it's not profitable to call
unfortunately this board just crushed the shit out of his pf range and I would just check it down/give up