Main question is what does theory suggest about situations where you get led into in 3bet pots on these kinds of middling boards?

And then if we get to the turn in this formation (not sure if we should be raising flop or not), when they lead again on a card that is so clearly advantageous to us WITH such a sizing, what in the heck is going on? Just call and bluff catch again on river vs QJs (?) or assume there are enough worse value combos + equity draws that it's worth raising turn?

Yatahay Network - $0.10 NL FAST (6 max) - Holdem - 6 players
Hand converted by PokerTracker 4: http://www.pokertracker.com

Hero (BTN): 120 BB
SB: 103.3 BB
BB: 120 BB
UTG: 121 BB
MP: 100.7 BB
CO: 127.3 BB

SB posts SB 0.5 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has Ac Tc
fold, fold, CO raises to 2 BB, Hero raises to 6 BB, fold, fold, CO calls 4 BB

Flop : (13.5 BB, 2 players) 2c Ts 9h
CO bets 4.5 BB, Hero calls 4.5 BB

Turn : (22.5 BB, 2 players) As
CO bets 18.8 BB, Hero