I’m curious to see what people might come up with putting the helmet scene at the start. The fact that he knows Palps is behind Vader’s voice is definitely an important question. In my edit I tried to solve this by having Kylo hear Palps’s voice when he touches the helmet, so basically it’s like Kylo was checking to see if what he said was true.
I think keeping the Vader helmet where you originally have it is best. It gives Kylo motivation to rebuild his helmet. And I totally picked up on him testing to see if it really was palpatine.