Mustardseed, I'm sorry that got so ugly. I'm not familiar with addiction issues so I won't comment on his state of mind at all, or what the right approach wrt that is.
I can say a thing or two about detachment, though.
First, I think what you're saying to your kids is right. It's really hard to parent through these experiences and I think your honesty is helpful and healthy for them. You are a good mom.
Second, detachment is all about letting him own his stuff without it impacting your state of mind. How are the financial issues and the R issues intertwined? If he's still at home and hasn't made a move to D, then what can't continue going forward? Even things like renewing a policy can be done in uncertainty -- they would be reworked in a D, but if he hasn't done anything about getting a D then you have at least several months to work with.
It is crazy hard to detach while you are still living together. I personally couldn't do it, so I really feel for you. But if you can get yourself to a place where you see him as a crazy roommate, it might give you the perspective you need to feel more detached and not rise to his bait. If there is a way you could get away for a few days I would do it. If his words and actions don't match up then you need to give yourself the space to really know that in your bones and establish a strategy for dealing with it that will give you peace.
Best to you, I'll be keeping you in my thoughts and prayers.
Me42, H40 D12, S8, S7 A revealed: 7/13 Sep 4/14; Agreed to D 1/15