[Black winter day]

a)You have to raise more preflop.I'd make it 70 at least.
You are OOP, and have 1 caller of a raise already.

b)As played, i also follow your analysis and don't instacall this, but i still call.First of all, UTG can really have anything here, from JJ to AQ - 44/25 are crazy numbers.And Bluffa can especially have anything - you both checked the turn when that second A hit and he might think neither of you have an A, so it's a perfectly good spot to bluff.He might also believe his weak A is the nutzzz now.
I wouldn't be suprised if one of them does have a set, but i think you are good here more than enough % of the time to make that call.It's true they both called the flop, so the have a piece of it for sure, but if that A did you more damage than helped, it's pretty much a cooler ,esp with their wild stats.

I would certainly fold AJ here though and in a lot of cases - AQ.