I agree 100% with Opalescent. Why not read Opening Up by Tristan Taormino together with him? Bring the book to bed with you, read him a few passages out loud, discuss, etc. It's a very good book and not over-the-top sensationalistic or preachy. If he's agreed to "work with you through this," then what's his problem with reading up on poly and learning what others have done to succeed and get over the bumps in the road?
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein