Hi rio, interesting hand. I fully agree with Bierbaer. Plus some of my thoughts:
You can even consider just calling flop so that you look like speculative calling overcards or so. Good reg will fold medium pairs already to your raise on flop. Always remember not to get isolated vs better. Raise only if there is value in worse hands. I mean
His call preflop is pocket pairs, AK, some SCs, maybe AQs, AJs if he´s bit looser. Here you block the A♥ on flop which gives you better info and backdoor.
Regarding donk betting generally
- from normal players/fish donk bet means usually weakness and you can raise them with air as they always fold on flop or to 2nd barrel turn. If you want them to stay in the pot, you call flop.
- from regular, donk bet is usually stronger. In 3way pots+ it is very often set. But in HU his donkbet is weird and may mean the same as donk from fish (e.g. small overpair). I would expect him to C/R w set in order to make you stack off on flop (as you may stack thinking he is on FD or smaller pairs). So I think his donk bet should be more FDs and weaker overpairs here (though it may be set as well, he just wants to bet/3bet). But he bet/called only. Maybe FD, SDs, maybe 77 ♦ , maybe just tricky with set
This hand generally
This is not a spot where you want to play for stack. You don´t have good enough comfort around his holding, to some draws you are not such a good favourite. He may have a set. Also if you push too hard, he will fold his mediocre hands. You will never get 4 streets of value (I mean 2x street on flop with raise and 2x bet on turn and river) from worse hands if you play ABC straightforward and I think you get max 2x value from medium pairs (hence I would call flop, check turn and get one value on river). You can use your skills to play bit tricky and get max from your aces, while always keeping in mind pot control. This is not your favourite spot, there will be better. And CG is also about what you do not lose. So do not push head against wall w AA.
Flop
- I would just call. You have position. It is not super urgent to protect, the board is wet, but you don´t want to inflate the pot and get into difficult decisions because you have big negative implied odds and almost none positive implieds. You don´t want to chase out worse hands. You don´t want to isolate against some range mixed from draws and sets (there you are not favourite).
- I call flop. Then my plan would be to call his lead on turn or bet/call turn myself. I could even check behind turn if I am afraid of being raised on turn. EDIT - yeah check back turn may be even better in vacuum. But it also depends on the momentum as well, what you think he is doing. On river I reconsider depending on community cards and what the timing tells tell me about my opponent.
As played raise flop
I surely check behind turn just to pot control. Then to your river question. If he bets, you call. If he checks I would tank a bit and bet very small like 1/4 - 1/3ish to get value from worse and induce. I call his C/R river. If he plays check turn and C/R river with monster I make a note for next time and check him back on river next time.
and therefore doing so not drawing to the nuts is quite bad IMO. Are 22-55 in your utg range of does he think they are in your range? 
