EP is 65/24 over 50 hands, but with an AF of 1.18.
i have $430. he covers.

he limps utg. i raise with [Qd] to $20 OTB. blinds fold and we're HU.

$40 pot. flop comes [4d][3c]. he bets $24 into me. i raise to $74. he calls

$190 pot. turns the . yuck. he checks, i check behind.

rivers the . he checks. i bet $120, leaving myself with ~190 or so behind.

thoughts?

No way he checks a flush to you twice. I doubt he has a str8, but unless you think he'll call that river bet with A5, 99, or 2 pair type hands...I just check behind.

Check behind or make a small value bet, like 1/5-1/3.