Nice insights. Couple of questions:
1. Did you also considered Leanpub?(I think they have a smaller fee) If yes, why did you pick Amazon over Leanpub?
2. Why didn't you used an easy to convert format? I mean instead of Word-like processors (be it Docs, Libre, Office or whatever) you could use Markdown, LaTeX or something similar, so you could convert into... anything: html, epub (so you could publish on iBooks as well), mobi, azw, pdf, word etc.