UTG is a reg(1k hands) with 7% openlimp and 100% limp-fold to raise so I prty much open with my entire button range

BB is a reg 21/13 with 4 3bet 1.9 AF 75% fold to steal over a sample of 500 hands. So far he had donked 5 times and always took a bet bet bet line with overpairs/sets (2 times) the rest 3 times the x/f. My thought process at the time was that QJ is at the margin and that my defend against a donk here is pretty close to any ace, sets, Q2,KK, and then rarely KQ,QJ with a backdoor draw(I open close to 50% OTB and the defence range I put is just about 16%)Villain's range on the flop imo is A9-AJ(He is 3betting AQ for value in this spot) KQ,QJ,22 and prolly some pairs under the Q.

Should I be defending here with QJs,KQs with backdoor draws?

Turn and river play is prty much str8 forward(maybe I should have bet more ott and less otr) and turned villain's hand up-AT-AJ,Maybe A9.

Plan with the current hand was to fold on a non heart Q,J turn if he bets.

Without some special history, I'm never folding to a donk bet on an ace high flop when I catch a piece (2nd pair or better like here). My reasoning is that, if villain held an ace, why would he bet OOP and risk losing the value of your cbet if he actually held an ace?

Rest of the line looks fine, though I'd definitely bet more OTT, probably closer to $0.44, which makes your current bet size OTR about right.

I call or raise w 100% of my range when he leads. Once he calls the turn I think potting river is just extremely bad since I think he's polarized between weak Ax or 22. OTR I valuebet any good Ax and I fakestall and make it 1/3p-1/2p if I have a hand I want to get a call with. If you had JTo, a PSB OTR is great.

Aight, made a note not to bet the river too much.

What if we had say A2-A6 in this spot? We're basically either loosing or splitting against him, so should hero try to get him off his hand, assuming the same turn and river? (with a pot sized bet for example)

Hands like weak Ax are hands you can afford to check back on the turn and bluffcatch with on the river should he have hands like KJ, KT or JT that he decides to stab once more with. I'm generally not interested in voluntarily putting more money in with a weak toppair when the middle card pairs, so I'd end up checking it down after calling flop. It's not like it's a scary board so I don't need to deny him any equity.