Wow, that went about as well as anyone could ever hope for! Don't worry about his delusions about who acted which way. None of that matters. He needs to see it a certain way to save face (or you can call it denial, but people who aren't alcoholics often do the same thing). I practiced saying things like, "Well, I don't see it that way, but we don't have to agree about it." Focus on the things you DO need to agree about--or that you at least need to arrive at a reasonable compromise on.
Shared physical custody isn't usually a great idea even when the parents are very cooperative. I think kids need a "home base." Of course, your son't safety comes first. Hopefully he is working on his issues.
See what happens--some people are able to pull off the divorce thing without too much agony. I was lucky enough to do it twice. Fortunately the only marriage with kids involved was from my first husband, who was sober.
Glad it went so well--I'd still get those preliminary orders in place ASAP.