SB is a reg and BTN is a fish. I have no sample on SB but FWIW he 3-bet 5/25 SBvBTN.
My thoughts preflop are that I think he is 3-betting wide to isolate the fish and that calling is better that 4-betting to keep the fish in. On the river Im blocking AK, AQ, KK, QQ and JQ. So in game my thought was that I had a good bluffcatcher and decided to call. But after looking into to it after it seems I was way off.

My guess is he bets for value with : AK(9),TT, JJ, AA, 89s (32 combos) .

The bluffs that gets to the river might be: Axcc, 50% of Kxcc, 97cc , A9s (19 combos).

So I need to be right 42% of the time when I call. If he shoves all of his bluffs his just bluffing 37% of the time.

Adding that 50NL regs are'nt balanced and very weighted to value when 3 barreling this should be a very clear fold. It actually surprised me.

I would like to hear your opinions on my assumptions, calculations and reasonings.