Hi guys

This is my first post so please don't rip me to shreds :)

Anyway this is a hand from 50$ PLO.I'm not sure how to put up hand historys on this so i'll just type it out.

5 handed to start.UTG(110x deep) opens 3x and I 3bet to 9x wi AdAs8s9c(140x deep)
Small blind cold calls(140x deep).
Flop is 6c9h9d 3 handed.
The UTG player leads at it for half pot and I decide to flat call to A:Keep in his bluffs.B:There is not much to protect against.
C:To look weaker than I am.
The small blind cold caller then decides to check pot it essentially commiting himself(IMO).
The UTG player folds and it is on me.What should I do?

Okay here is some background on the small blind.He is very tight.He's got that ABC tag from HM Manager 2.
His VPIP is 20.PFR is 11.So yeah pretty tight.(Over 651 hands).
So my initial thought process was that the leader looks potentially weak as he might want to stick in a check raise with a 9xxx.
Also I look pretty AAXX heavy as I 3bet a UTG 3x which I do a lot with AAXX.So a good spot for the small blind to check raise bluff.
Of course this thought process could be okay for a loose aggressive player who makes moves.However this guy is tight ABC player
so we can rule out a bluff.

So if he is not bluffing what does he have?

He cold called pre so that is pretty strong for him but not for this board texture.He has a lot of high run downs/double suited hands.
KKXX double suited etc...So I was struggling to put him on a full house.He can have 66 plus pair hands or 6789 double or single
suited but that is about it.Hands I beat he can have are 789T/89TJ/9TJQ.So my problem is that this guy is so tight he might not even
check raise those hands and just check call and wait till he hits a boat.So if he only check raises boats I guess I have to fold as
I am only 14% vs 6789 and 26% vs 66/pair hands.(rough estimate).His raise Cb stat is 0(11) IP and 0(21) OOP.Against the other range
of 9xxx hands I think he has but am not sure he will CR I have roughly 60%.By typing this all out and thinking it through i think it's a fold
but I would love to hear some feedback/suggestions to what you guys think.

Any help on this would be greatly appreciated :)