SUPERNOVA

I think overall the hand was played optimally all the way through.

Pre flop we definitely have odds to call from BB IMO and then once we smash the flop like this, it's an easy stack off. It's pretty rare we will run into this hand but even in this case you weren't drawing dead unless he had something like AcXcKK

Just as everyone else has said, your hand is under repped, its an easy call here. I'd expect to win it more often than not as well as chop a decent % of the time.

Don't put too much stock in table dynamic. It's an easy fold for a bunch of reasons:

1) Your hand is not very strong and doesn't flop very well.
2) You don't get to close the action. Do you really want to end up sticking it in here in a multi-way pot?
3) When it doesn't get stuffed in pre, you're likely to see this flop multiple ways. When you actually do flop fairly well, you're likely to be dominated on most draws.
4) You only have 3bb invested, there will be better spots. There is absolutely no point in going crazy here.

Fold flop

"Villian is a decent reg who 4 tables, plays most hands pre but is an absolute rock post. He only ever value bets and he just doesn't go after pots at all, doesn't c-bet without any equity just checks and folds to a turn donk."

If this is your read then folding river was the correct play and fairly easy. What would he donk the flop with? KKxx, 44xx, 22xx, some sort of K4xx, K2xx, maybe some type of 2345 hand, decent size flush draws, etc.

Now, once the flush comes in on the turn but the board pairs, we can assume he might continue with JcTcXX type hands and also the same KKxx, 44xx, 22xx, K2xx, etc. We can expect him to check K4xx.

You have now called two streets, so once he bets again, I'd say it's pretty safe to eliminate JcTcXX type hands. You have the nut flush so we know he obviously doesn't have that. He's not going for 3 streets with a smaller flush. We can safely fold the river as his range (based on your previous read) is almost certain to beat our hand, this consists of:

KKxx (some KK hands that do not have a suit will flat here PF IMO if he's a good balanced player).
44xx
22xx
K2xx
2345

What can we beat here besides a total airball?

VPIP obviously doesn't matter since IMO playing about 95% of hands HU is optimal if we have any edge at all on our opponent. You need to look for tendencies. A HUD can help your PLO game in some ways by helping you identify some of these tendencies if you're not extremely perceptive but HUDs are not nearly as important or 'vital' as they are in NLHE. It is not a substitute for plain old paying attention.

Agree with everyone who said that I would not necessarily 3-B this pre. I'd reserve 3-B AAxx when I am at least single suited with connectors.

As played, you need to bet more on the flop. Your sizing is begging for a raise as a bluff or with equity (in this case we'd be lost and have to just fold) It also allows opponent to continue with marginal holdings that can easily catch up on the turn/river and again, we'll be lost. I would B/F at the minimum 2/3 pot but closer to 3/4.