Very good (and funny!) summary overall.

I've read the book so some of your questions are answered there, things that the movie just couldn't get to.

The biggest departure of the movie from the book was the ending IMO where Chain rides off into the sunset on a sandworm. In the book she accepts the political move. It's quite interesting as this is literally the last line of the whole 800+ page book so I found it quite surprising (I'm still undecided how I feel about it):

“Think on it, Chani: that princess will have the name, yet she’ll live as less than a concubine—never to know a moment of tenderness from the man to whom she’s bound. While we, Chani, we who carry the name of concubine—history will call us wives.”