And welcome to the greatest place on earth for those with aliens for spouses! It sounds as though your H is definitely in MLC (and it's only when they're starting to come out of one that they can finally see that's what it was). You are surrounded by people here who know exactly what you're going through, because they've heard all the same things from their spouses, and suffered the same kicks to the gut. Read their stories, and especially read all the resource materials.
In a nutshell, your H is probably depressed (was there a trigger 3-4 years ago?), is looking for happiness outside himself (enter OW), and is on a journey to repair core hurts suffered during his childhood. The good news is, he will probably emerge a better, more self-aware person. The bad news: this all takes longer than you'd imagine possible.
In the meantime, all you can do is focus on becoming the person you always admired most and wanted to be. It sounds as though you're doing great, cutting out unhelpful behaviours, learning to detach, getting new interests, and showing him that you're determined to move on. This all becomes harder when they're nicer, so read up here on what to expect and how to respond to it.
