"What I need to know now, is is it possible for me to detach and give him the space and time he is asking for and both of us live in the same house? I just don't know if it is."
Yes and No. It can work... the other person has to be somewhat receptive to it.. or you have to have really thick skin.. and have your head on completely straight. You will have to think and respond under a great amount of stress.
The other way it goes is you two kill each other.
Detaching with physical distance.. is not always a bad thing.
"He feels terribly guilty that I've lost more than 20 pounds and am a mere shadow of the person I normally am."
Now this hit home a bit.. I use a picture for my avatar.. the picture show me standing on the beach.. a wave just passed.. and all you can see is my shadow. To me it just said.. the shadow of the man I used to be. I took that picture.. about 2 weeks after I moved out. The meaning today (of the picture) is still exactly the same as it was when I took it. Yet it means something completely different. When I took the picture.. I was angry, sad, lost, separated, broke, homeless.. to a point. I have lost all that simply because the separation was good.. it put a quick end to a big issue me and my wife had.. from there we sorted it all out. So I am still a shadow of what I once was.. I am much happier with what I see in that shadow now.
"Why can't I just get it together before I lose everything?"
Some people need to get to the bottom.. it has a side effect of making you look up. You loose "everything" so you can start over.
"I don't want the separation, a possible divorce, etc. But he says he is always going to be in my life. I think I just need to accept this and stay quiet. He knows how I feel; I'm sure I've made it clear."
You can't cling to something and expect it to change. If you hold onto your kid that first day of school.. they will never get on the bus. You know they need to go to school.. so they can learn to spell and grow. You have to trust that things will be OK. Somehow.. some way..
Keep an open mind.. as hard as it is to do. Thats all you can do.
Keep your head up.. and always...
Relax Eat Think Act normal React.. Smartly. Do something different. Emulate. Do Work.