AA on pair board in 3bet pot

On the turn, when CO raises, I think he has KK, maybe TT, maybe 77. You only beat a pure bluff.

Maybe a bet/fold would be better at turn (like 1.2 sizing) cause I don't think he would shove his wraps or FDs so his range then is 7xxx and fullhouse-heavy.

If his range is 7xxx you have around 16% equity and I don't think he raises here with a draw. I would bet half a pot on the turn and fold if he raises.

With given effective stacksize on turn after i bet, i think this is a call. Maybe if i would bet smallissh i could fold. I dont like small turn bet because this might indicate bluff from some players, and i cant b/c probably.

I decided to bet on turn because he apart from 7x, kk could have something like, Tx (kt, qjt, 89t, maybe qq), and I bet on turn for value.
I am confused with my tought process, i dont want to learn bad habits.

Most of the times players don't like to call with weak hands on paired boards. When he calls the flop, the only hand that can give you value for more than 1 street is pretty much KK and turn hits that. He could be drawing, but majority of the players don't like to draw to a paired boards. I would definitely check-fold the turn, as his range is crushing you even if he has draws in it. If you have reads and notes on the villain that he likes to call with draws, then it might change the situation.

Flop bet is good, and without any further reads or information check turn. Barreling here without reads is burning money in the long run.