Opp is not a noticely bad player but probably not great either.

1. Folds to me in the CO, I rase [6s] to $4 and SB calls.
2. Flop [Th][2s], pot $9. SB checks, I bet $7, SB calls.
3. Turn , pot $23 SB checks I check behind.
4. River , pot $23 SB leads $15 and I raise to $45. This coo?

I feel like I'm repping quite a lot of hands that should crush his range. J9 got there and QK is calling, but I don't feel there's much else (except for maybe a random [Ks]). Thoughts?

Once you check behind on the turn, nobody ever believes you have anything. I make this exact same play with [6h] all day and get paid off every time.