Hand 1 - call all day, pot odds! Though I must admit his turn check of the K is somewhat scary and if he had bet more on river I'd be inclined to fold. I'd expect him to bluff the K on the turn if he was going to be bluffing.

Hand 2 - Wow, bet everywhere. If you don't think you'll ever get called by worse when you spike your A with AJ, then why even 3-bet AJ? Bet flop because you're betting almost your entire range of 3-betting hands on this flop. Bet flop, jam turn.

Hand 3 - yah if he's calling a lot of 3-bets then i'd probably 3-bet him more with KJ/QJ/77 type hands than polarizing my range. If he's calling too much, that means he'll have some crappy K6s hand vs your K2s when you spike your K and stuff like that. I agree with marshall with regards to merging your range against someone that is calling 3-bets too much.

As played, I probably end up playing it the same in the moment, even though I agree with nutsinho that there aren't that many hands that called that flop that will now fold the turn. I just don't like c/c here too much, since there isn't enough money behind if we do hit. If you have reads that he calls flop bets in 3-bet pots but folds turns (which a lot of players do) then I'd fire this turn.