We are the same age and I have D17 and D15 that live with me 24/7.
I have been doing temp work for almost 2 years. I don't have all of the time I would like with my D's and are their issues behind all of this mess? Yes, theirs, mine, their Dad's. All of it sux.
I had to get to a point (in my own head) where I was truly looking out for myself and my D's without thinking about what was going on with him and if he was coming back or what.
It's hard to start over. I can think of almost anything else I would have rather done. I haven't always done it well, but I have managed.
You have the added bonus of having him as a business partner. That's really tough. Esp since he seems to be flaking out.
I like what Lostforwords had to say about plan D. I know how hard it is to focus on all of this when certain thoughts crowd out others in your head.
I have taken up different activities in the last few years that help me clear my head and think. Does it always work in times of high stress? No, but it always helps.