Villian is running 33/26 over 46, 1/11 3bet and 67% aggression frequency.

Merge - $5+$0.50|<> NL - Holdem - 5 players

UTG (UTG): 1,730.00
CO (CO): 2,855.00
Hero (BTN): 2,965.00
SB (SB): 4,180.00
BB (BB): 1,770.00

SB posts SB 100.00, BB posts BB 200.00

Pre Flop: (300.00) Hero has A 3

fold, fold, Hero raises to 400.00, SB raises to 600.00, fold, Hero calls 200.00

Flop: (1400.00, 2 players) 6 3 T
SB bets 400.00, Hero calls 400.00

Turn: (2200.00, 2 players) Q
SB checks, Hero checks

River: (2200.00, 2 players) K
SB checks, Hero bets 1,965.00 and is all-in

We have to defend this 3bet cause of odds?

I kinda think he mostly has hands like 88/JJ or some spaz 3bet when he checks turn. Since he checks again on river, I think most of the stronger hands are out of his range. Ok turn into bluff on river?

Pre flop there is no way that you can open shove this, would be a very bad ICM play. Open folding is way too nitty IMO and limping obviously sucks. So I like the play you made making the min raise. The min 3 bet from SB sets some alarm bells off but I cannot see folding here, for appearances if nothing else. I would also make the flat in position against the min 3 bet.

Flop is kinda meh but I would call and evaluate turn as well given these pot odds. Also I think even though it was a min 3 bet that he can have hands like AK, AQ in his range plus against this type of player in a $5.50 sit n go on Merge you have to assume that they have some weird random crap at least part of the time.

At this point we have ~10 BBs left in our stack so my goal here most of the time would be to keep the pot small get to showdown without committing more chips if possible. I would tend to check the turn back like you did. I would also check back the river not having enough confidence that this type of player can fold a hand like 10 10 to a river shove after we flat the flop and check back river. My thought would be that we have some showdown value and a 10 BB stack to continue with if we lose the hand. So basically our edge in future hands makes me want to show this down and either beat his AK or continue with a 10 BB stack.