Incredible submission! I love the three competing NPCs as a device, especially the trust fund weapons dealer.
This is just my personal opinion, but when I see a star destroyer/end of the world or universe type plot device my eyes glaze over a little bit from its overuse. But other people clearly love it! One thing to consider, I think part of why the original Star Wars trilogy worked is because they were trying to stop the Death Star after it destroyed Alderon. Same with Avengers Endgame Part 2, Thanos successfully did the snap. I don’t know why, but it counterintuitively seems to raise the suspense and it might be worth setting the Star Killer adventure post first use.