This is rattling my brain. Ive been looking at it for a while now so here is what I think...
I think the BTNs range is a lot strong because of his actions. He limped, raised and usually when I see this I assume its premium hands so I would say that he would have a range of maybe JJ+/AK esp cos fish like to flat with big hands to trap us.
I think the UTG range is probably weighted towards hands like AK/AQ cos of the flat call from your raise.
Personally, I like the shove cos were OOP and dont want to go to a 3-way flop. If we shove, we can isolate the BTN who only has ~50bbs anyway and cos UTG has played the hand kind of passively from what we can see I think it he is going to fold more often than not and even if he does call were still in good shape against his range.
I hope this makes sense but its probs all wrong