1. Saturn wormhole. Correct me if im wrong but i thought one of the established points throughout the movie was that there seems to be some higher dimensional "them" who are pulling some strings in order to help out the 3-dimensional Earth people. They have their own unique limitations within 3 dimensions, so the way they help is by providing prompts and physical opportunities for the 3Ds to do their part in saving mankind. The "convenient" usefulness and timing of the wormhole near Saturn and anything else "they" do (like fashioning a way to use a Matt Mc as a go-between with the bookshelf) is only sensible.

2. Let's say I'm mistaken on #1. Stories are kinda like really elaborate complex poetry. Things will rhyme and connect in ways meant to evoke an experience to enjoy or feel within your humanity, not to provide an alibi for a jury. If it was an old traditional folktale, you wouldn't complain, but modern day critics unfortunately expect movies and novels to intrinsically detach their nature and purpose away from that ages-old tradition of human storytelling. We're too jaded.