Hi, I'm fairly confused with this hand.

I had trouble interpreting BTN's pot bet OTF - I find it hard to believe for him to limp Ax / 33 pre with short stack in SB. He could be strong pre (AA / JJ / maybe AJ+) trying to induce SB to shove weaker hands, but not sure how effective this was anyway.

I suppose I could ignore the SB's shove as he should be getting it in with probably any J.. so the question is how good is my top pair vs the pot bet from BTN?

In the actual hand I folded as I was either way ahead or way behind. It looks a bit marginal and I was still with a healthy stack if I fold. If I called and c/f turn, I could be foldng the best hand too as I don't have much A in my range either right?

well played. you probably lost the minimum here. Preflop checking is fine and thats what i would do readless. With reads i may make it 4xish pre. Post flop no other choices with that action and stack sizes has to be a fold.
Like you say your tpnk is very marginal and you can fold and still have nearly 30bb seams very sound reasoning to me.
Its hard to interpret their ranges readless. Stats on button would really help as open limping from the button is one of those moves either done by fish or non standard regs. The standard mass grinders /stabled players dont really do it.
So im assuming BTN called as sb has no FE with his shove so you know what they had and your posting saying your confused so im guessing your ax was good and they had jx or maybe pocket mid pairs but regardless of result i think you played it well.