As for the GTO aspect of his play....it's hard for me to answer completely accurately because I don't have that much experience playing 40-50bb ante HUNL, it's a rare game and is basically only played when you get HU in a tournament. Additionally, the game is played very differently in 2016 than it was in 2007. But I would imagine I have some sort of limping range and a wide value raising range (most of my Ax but I do limp some of them) and am folding <5% of hands due to the ante. After I limp I think Ike raises most of his Ax and all of his broadway hands. This is important, because that means his only gutshots are 23 25 35 (KJ JT KT all raise), and his only other "air" c/c hands are hearts that decided not to c/r, and I think he c/c Qx 4x and his king highs as well.
In 2007 I would likely be cbetting this flop with my entire range after he checks back pre. In 2016, I would likely check some Qx and some 4x back on the flop, reason to bet some Qx on the turn is that since he likely raises most or all of his Ax now my Qx is ahead of almost his entire range so I can bet it freely.
The turn K pairs some of his c/c range and when it goes c/c that eliminates 2 pair from my range.
On the river Q, he needs to bet since he has the nut low, he bets all of his 23 35 25, bets quite a few hearts (likely checks the Jx Tx hearts since they have showdown value), bets his Qx, whatever Ax he has, and probably checks his Kx. after I raise he knows I have no boats but he can have Q4, but from a GTO perspective, since my range is {Qx,bluff}, I pretty much have to commit to calling off Qx otherwise I am folding range.
So I think the deciding factor here should be blockers: he should 3bet hands that don't block my likely Qx hands. I'm probably raising most of my good Qx preflop, and probably limping the Q2-Q6o range. He shoves 6 combos of Q4, and can probably shove a few extra combos of hands like Q9/Q8 that he limped back (let's say he can shove 25 total combos) but knows are ahead of my Qx so he can shove probably about 8-10 bluffs, and I would probably do that with the hands that only have one 2-6 in them (he probably raises 78hh 79hh 89hh and checks river with Tx Jxhh), like 92hh 93hh 95hh 82hh 83hh 85hh 72hh 73hh 75hh. Probably not GTO 3b shove, but very likely that my raising range is weighted too heavily towards bluffs and his rebluff is still +EV.