Sounds like you are getting the pieces of the puzzle put together. It's great that you and your SO are developing and understanding with each other.
When you get done with "The Ethical Slut," you might want to consider also reading "Opening Up," by Tristan Taormino. It's another great book about poly and responsible nonmonogamy in general. Covers a lot of bases.
I wish you guys the very best.
Love means never having to say, "Put down that meat cleaver!"