Small blinds flat calls a 3 bet.
Board presents a flush draw.
Hero bets on the flush draw 10 high board.
Turn presents a jack.
Check Check
River presents an off suit board pairing 3.
Hero Bets
Small Blind Check Raises.
Given small blinds stats, its possible he has a 3
Its very possible he has a worse2 pair.
It is most possible his manic aggression with few hand doesn't respect a cutoff 3bet.
My initial assumption is call.
I will run some numbers now and re evaluate.
Here are hands I think a loose preflop and tight post flop player might call a 3bet AND continue on this flop with.
99+,33,AJs,AcTc,AhTh,AsTs,Ac9c,Ad9d,As9s,Ac3c,As3s ,QJs,JTs,T9s,98ss
At this point you have 58.4% 41.6% equity on the flop.
Check Check Turn brings the equities to 50.5% 40.5%
The river gives you the best equity edge of 58% 42%
In other words against this range and apparent aggression you have
odds to call.
Your biggest dilemma here is the check raise all in river.
Are you playing with 100 buy ins, or do you have 1/4 your roll at the table?
If you are well bankrolled I think this is an easy call. It will give you valuable information on what villain is willing to flat in the blinds, and insight into his river play.