Hi, I play NL10 and NL25 in a very little room, full of fishes.

However there's one regular who makes things interesting, it's loose aggressive and in 15k hands he folded almost every 4bet to my shoves, so there's definitely 4bet bluffing and 5bet bluffing on both sides.

I'm pretty confident with these dynamics (maybe I'm wrong, but nothing bad happened aside from occasional coolers). Problems arise when we both have 200bb or 300bb stacks. I don't think 5betting all-in would be good with QQ and AK, and even KK I'm not sure he can call with worse.

5-bet size
We both open 3bb, we usually 3bet around 9-12bb, and we both 4bet 2.5x around 22.5-27bb.
What is the right 5bet size? Around 50-60bb? Or should we 3bet and 4bet larger?

5-bet range
With 200-300bb I think I want to stack off only with AA, and I don't want to 5bet / fold KK against such aggressive player. Ok: I don't want to 5bet / fold KK because I would feel stupid... So I would flat 4bets with KK and worse, and 5bet AA plus some bluffs (like A5s combos). How many bluffs depends on sizes and stacks. I made a spreadsheet, basically bigger 5bet means less bluffs, bigger stacks (6bet shove) means more bluffs, more equity for a 6-bet bluff means less bluffs in 5bet.

6-bet range
AA and bluffs, in theory. I can do 5bet bluff and maybe he can do, but can we do 300bb 6-bet shove bluffs? I don't know. However, there's a little possibility he could overplay KK or AK and just shove it. Reality: I think against a 50-60bb 5bet we would both flat to play and pray postflop. However this changes calculation of value/bluff ratio of 5bet. I guess I can go with the highest value/bluff ratio and maybe adjust over (lot of) time.

Do you agree?
Would you just avoid 5betting?
Would you ever bluff a 200-300bb shove?