Agreed with what dgi said. Some super nits only raise AA/KK. Some only raise QQ+. Some will throw in JJ and/or AK, and then their range is more like a nit-TAG. A standard TAG is likely raising 99+/AQ+ from EP. It's a continuum.
Most players will have AK here, and every time they are holding it, raising all-in is an incredibly strong play.
We are freerolling all combos of AK, so every time he calls our $159 bet we make $32.
It's even better if he's a weak-nit and finds folds with AK. Every time that happens, we make $210.
Obviously, if he has all 6 combos of AK and folds them then getting it in is profitable.
Sets we are obviously doing terribly against but we do suck out on them 1/5 times. We lose $259 four times for every $600 pot we win, netting us -436 in these 5 pots. We are only losing $88 each time he holds a set.
Ok, so if he has AK all 6 times and folds them we win 1260. And we lose 352 to his sets (4*88) so – assuming he has all combos of AK here and folds them – going all-in will net us:
NINE HUNDRED AND EIGHT DOLLARS!!! Gasp. That's if we get to play the hand ten times in a row though. :P If he calls we are only making 32 six times and that won't make up for 88 four times, so it's a fold.
So yeah, we would have to have a very specific set of reads: 1) he has AK here, 2) he folds AK here. If those were our reads, shove away. Without knowing both of these folding is best. This player sounds like he doesn't have AK here sadly.
Players who would bet/fold AK here are not rare, and in fact raising would be a great move to use against a TAG who can and will bet/fold AK when the flush comes in.
No, he doesn't have a flush or two pair or a bluff here. His range, with this action on this board, is exactly: AA,JJ, and possibly AK.
By the way, knowing how a player plays AK is critical to understanding a player's style and how he thinks. I'm surprised we don't know how this player plays AK. OP, have you ever seen this guy showdown AK in a pot he limped, or in a pot he raised?