Cool find, I love the Sith whispers!
Well I think you’ve done a solid job so far making it feel like it could’ve been a part of the movie. I agree a lot with jarbear’s last post regarding it. In order to not reuse those shots of Ben looking up, just cut his and Rey’s last interaction, that way you can just use it for his reaction to the radio. I also think making it briefer, and just having it say, “Find me…”, or perhaps, “The time has come… find me…” might have a more subtle touch. And like jarbear said, having the dialogue somewhat distorted could lend to some mystery regarding who exactly is sending the mystery. Your hypothetical first time viewer might be pretty sure it is Palpatine, but still enough room is open for speculation.