Villain is 20/15/3.4 over 135 hands.

I would just check behind. Can't see you getting called by worse.

i would only call flop if villain has a tendency to super aggro and barrel a lot or if he bets flop, gives up on turn a lot. I think peeling flop is fine but you should fold turn, your just burning 12bb calling there. Raising flop also isnt terrible either imo, villain flatted OOP and donked out, generally i dont expect them to be strong, plus it makes it easier to get to SD.

if villain never goes to SD and you think he can fold Tx then i would bet but as played just check behind.

looks fine if hes bad
if hes a reg type tag turn is abortion

Looks fine if you checked back the river.

Yeah, at 4NL I don't really like calling the turn vs someone whose barrelling tendencies are effectively unknown. What's his donk flop %?

I fold turn unless V is a drooler

What hands are doing this on OTF & OTT? I would think that a set will make it bigger OTT or check in hopes of raising. A set won't want to fold out AK ui.
TP could easily be doing this, which at the time made the most sense OTR when he checked a broadway card.
The only realistc draw was 45, but if villain is calling a raise with 45 from the sb, I think it would be 45s which is only 4 combos and kind of suspect IMHO. I think the most likely range of hands that do this are 910s-A10s, or pocket pairs, that didn't hit a set, 44-JJ. If this is correct his range is weighted towards TP hands, so I can see why there are the responses of folding the turn. I think calling the turn is close and I had some trouble with that at gamespeed.

EDIT: Once I called the turn, my plan was to fold UI to a river bet

I normally just call the flop and fold the turn in situations like this. When they bet the turn I just put them on a set or at the very least a ten, and safely fold.

It makes my decision easier since I don't want to be debating that they could be donking a draw, and even if they are donking a draw, are they doing this enough?

fine as played as long as you checked the river back, i assume he has a weak T or 77's or 88's or something, if you bet this river he'll fold all that you beat and call with all that beats you, so no value in a river bet.

I guess that's what notes are for, as well as flop agg%. This line is jsut very strange. Why would a set want AK UI on a 10 hi flop to fold? There's no draws out there that HERO could reasonbly have and unless villain thinks on level 0, he must know I am going to c-bet most all flops. This line just doesn't make sense to me, but then again, I am currently a reg fish.

check behind river..
vs reg i think you have to fold turn...