Hi DogTired, well I'd say you're right it does seem to be "all about him", but use that.......it is his problem............it really doesn't as much need to be yours. If he's doubting you, it doesn't need to be your responsibility to try to persuade him of...........afterall you have explained the situation in an understandable way.
If he's upset with you, if he's not supportive, if he's negative..........you've done/you're doing your bit in leaving the door open for him to alter his behaviours........you've made it clear where you're coming from, what you want/need and have offered him support too..........if he's not willing to work with you then let him isolate himself, let him feel the way he's feeling and focus on yourself. Focus on what you need, focus on what you can do with support to work through how you're feeling, what's right for you. Your beliefs, feelings, thoughts really don't have to reflect his.
And focus on the people who are really going to be there for you, he need only be "a small part in the puzzle".
Realistically it would be better if he was gone............but I'll let you consider if maybe the kids (although initially upset) may actually feel better if he wasn't around right now, I mean there's every chance they're picking up on his negativity........the way he's behaving and making you feel already, and with his attitude/lack of understanding etc perhaps those things are filtering though in the way he actually is with the kids??? Something to think about, hey???
But I have got to say, real kudos to you for perusing the IOP treatment, don't let anyone stop you from doing what's helpful to you in working through this depression. I see real strength there, you hold onto that!!!

Alison