UTG - 8k
Fish(MP) 2500
HERO (button) - 3000

UTG spewy over aggro kid that gets it in way too light deep Raises to 30.
Fish(100% vpip and 100% call flop and most turns) Calls
Im button with AKJ8, K8 suited and 3 bet to 125
UTG 4 bets to 400
Fish calls
Hero calls. (Bad call? UTG range is likely any run down or rundown with a gap, or aa)

there was a random short stack that called/went all in for 500

POT 2k
flop AT6r.

checks around to me
Hero bets 500 (into new side pot)

UTG quickly calls
Fish folds

2k main - 1k side

Turn 6o

UTG insta shoves for my remaining 2k.
hero?

thoughts on all streets needed here. thanks!