I agree that this was an infodump of variously loosely connected vignettes with no real resolution or tie-together. I can't say that I disliked any of the ideas involved, but the work as a whole left me flat. Regarding the ideas, I'm a huge fan of relativity and all that is involved, I'd love to see a very good story about relativity, and not just time dilation, but the idea behind relativity that this story touched on, that being things look very different depending on your point of view.
As for the boson gun: Maybe the gun had a poor targeting system, and instead of piling a whole bunch of mass in one place, it kept accumulating mass until it hit something akin to Chandrasekar Limit, and collapsed into a universe-ripping black hole? As for why it only affected certain people, I have no answer given the data.