if you think that donking will cause him to lose his brain a bit then it's a fine spot to donk. Just be aware it's not an easy strategy to execute overall when you do it (but I guess it doesn't matter)
r.e pre-flop I think the "deeper the better" isn't always true for calling 3bets (oop speshly) with weaker hands, I thnk as a general once you get past a certain depth (say 175-225big blinds) this is the optimal stack to start opening up your call vs 3bet range. Once you get 400+ I think you get a lot of reverse implied odds + you're going to find your hands way way harder to bet for value down the streets.
Definitely agree on the difficulty in a long term strategy but its not really relevant here. I have a very splashy image because i 3bet light, and have pulled off big bluffs before. My days now consist of valuetown and call downs, but people still won't give me credit, and if they do, they will probably ask me/a mate about the correct reactions. Notes taken on roi @ 400 bigs deep, need some time to discuss but the concept makes sense, ty as always
edit: vs specific opp, deeper the better is probably true despite positional advantage. Hes tight and ok, but no creativity or real hand reading when not on form like the moment.