I'm trying to think through my hands better by evaluating the opponents range. Part of that is thinking through the bet sequences as well. I'm going to make some mistakes but sometimes I'm in marginal spots and that's where I'm trying to learn. Onto the hand:

PLO10
Hero (BTN): 270BB with JJT9 single suited
Villain (UTG) 100 BB. 18% PFR. No history but I've lost 3 big pots to villain and the biggest one I've won is $1.50. I didn't have time to see each hand I had lost but usually with a player I recognize we are about even in terms of wins / loses of 100BB stacks.

Pre-flop. UTG Raise $0.35, BTN calls, BB calls. Everyone else folds. I'm trying to 3bet more often but I think my hand needs to be double suited for 3bet and single suited is just a call? Villain's range is pretty wide as they have raised UTG before with 8543 single suited.

Flop ($1.10): AJ9 rainbow. A good flop as I hit middle set but I hold a 9 making it unlikely villain has A9, AJ or 99. Best I can hope is that villain has AK, AQ, KQT (which I also block)

UTG bets 0.83 (75% bet). Hero??? Villain may cbet a wide range of their hands and this range hits an UTG open. As I mentioned, I have middle set, block 9's, block AJ, A9 and QT is blocked. If villain opened weak I won't get much additional value out of them, if they happen to have a wrap then I want them to pay on the flop and then I can shove turn to play for a big pot. It's unlikely due to blockers but that's my strategy. I decide to raise to $1.75. I figure this is a small amount that perhaps villain can call with AK, AQ, AKQ. BB folds.

UTG then immediately raises pot to $6.35 effectively making this decision an all in one. As I mentioned in my analysis above villain's range that could do this is pretty much limited to AAxx, 99xx or a wrap. I block the 9 and wrap though... what should I do?? I think villain shows up with AA here more often than 99.

Adding an edit: I've called these every time the past 3 days ( about 5 instances) and in each case I've run into the highest set

go all in

Who hits this flop harder UTG or BTN? Not sure you're 'allowed' to raise this flop since UTG has such an nuts advantage. If you were to have a raising range JJT9 wouldn't be in it. AJ**, AJJ* and JJQT are bettter candidates. As played, think we can make a really nitty fold since we are pretty far down in our very narrow range. Of course I could never make this fold irl.

I'm pretty sure you're not allowed to raise flop here yea.. Call

If I call flop what's our turn strategy on:

1) K,Q,T,8 turn cards? I'm assuming if it's bet to me 50% or less I call? If it's checked to me then I bet 50%?

2) A9 if checked to I can try a small bet but if it's bet into me I'll fold?

3) J I'll be happy with

4) That leaves 765432 as blanks plus even any of the above can introduce a flush draw.

I'm not very comfortable with the turn in situations like this because so many hands can introduce different nuts and the blanks still leave me guessing if villain is double barrelling or has AA. Any suggestions on how to learn turn strategy better?

That's PLO.
Never bet big or raise flop because you want to avoid uncomfortable situations on turn/river. My only advise on turns is to use all 4 cards. Set is great and all, but without an Ace and blocking the 9 our hand will not see showdown 100%. We do have a straight blocker so we could make some hero calls if straight comes in on turn or river as villain should be barreling with AQQ* AKK*.

Work on your flop strategy first.
You have no draw and don't have the nut hand. Play a small pot. Call.