ATo top pair BTN vs CO facing 3-barrel

I like your line all the way. 3bet pre as a bluff is an option but I would do that with hands which are more appropriate for this like suited connectors or suited aces which play easier postflop and are less dominated. And also against tighter opponents where you can generate decent fold equity. So flating IP is just fine. Any info on villain btw.?
Postflop calldown flop and turn makes sense since the board is dry and you dont need to protect much. Folding is too weak and raising would isolate you. The runout is not too favorable and I would fold river as well. We basically beat bluff only in this situation and I think that on NL5 not many players will be able to bluff 3 streets, at least not often enough. So for me a good exploitative fold. You would most likely see a better hand in showdown.

I like your line postflop.
Preflop I am not a huge fan of coldcalling off-suited broadways since they play terribly mwp and without initiative. In addition you have to fold against any squeeze plays. Therefore I'd rather put ATo on the BTN vs unknown reg CO OR in my 3b range.