I'm at $300 and villain is a really aggro middle aged LAG with $500 behind him. Seen him semi bluff, 3bet a ton, and whenever he cbets the flop it's usually an overbet because Hawaiian Gardens casino uses $5 chips but the flop pot is all $1 chips so there's like 10 $1 chips in the pot and in order to get any respect you have to overbet flop everytime because the donks see a 2 $5 chip bet and say "hey its only 2 chips and there's 10 chips in the pot!". I myself overbet the flop a lot here because of this dynamic so an overbet doesn't mean anything in itself.

Hero has KJ in the SB

Preflop:
2 limps, CO raises to $12, 1 fold, Hero calls, 1 fold, MP calls.

Flop ($34): J42
Hero checks, MP checks, CO bets $45, Hero calls, MP folds

Turn ($124) A
Hero checks, CO checks

River ($124) 8
Hero checks, CO bets $130

I checked river to induce cuz I don't think he calls me without a J or A, but that's a really big bet. Still, seems like a snap call to me after he checked the turn with 2 flush draws on the board, or am I wrong?

Don't flat Kojak in the SB. Raise or fold, depending on your feel for the table and villain.

You checked to induce on the river? Well, you succeeded. LAGs bet at dangerous looking turns. Bad LAGs try to get tricky and check when they hit a hand, which is -EV for them. I'd fold, but frankly I don't put my self in this position often.

Fold preflop even though it's likely to be multiway and KJs is way way way ahead of CO's raising range? Guy was raising 1/3 of the hands preflop.

On the turn, since this guy is so aggro and he knows nobody at the table respects his bets, my thinking is if he had an ace he would have to bet because no one at the table is folding a J or a flush draw there in a million years.

given reads on villain i raise pre for value and to iso. make it $35-40, then cbet flop 2/3 pot and reevaluate based on villain's reaction

also what is your image at this point? if villain views you as TAG you have better FE post flop, so raising pre is a good idea (we can often rep overs by cbetting if we don't connect). if you have a spew or aggro image for whatever reason i would fold pre because in that case KJ will tend to get you into trouble post