Ok, Rob, here's what I am thinking. In your W' case, beyond the normal issues of depression and maybe some substance abuse (mainly alcohol) that often afflict the WAS, your W is dealing with a severe eating disorder made worse I would guess by this sitch. In turn you are faced with that complicating factor.
Normally, I (and obviously UD) would suggest that more time and patience is needed from you. That may be the case, but this ED is throwing a BIG monkey wrench into things because I guess you feel that standing by, just being patient and waiting her out, you are contributing to her declining health and maybe death down the road.
I think I am WAY out of my league in terms of rectifying DB with what to do in the case of an ED. I know you were reading a lot and visiting boards about the ED and what to do. What did they say to do? Is it something that can be rolled into DB or your overall R strategy or was it a lot of confrontation? I really think you need to find a way to put your W's health at the forefront of all this and like UD said (I think it was her) allow the R stuff to fade. Do what the ED folks say to do to the best of your ability FIRST before considering the DB ramifications.
I know it's hard because I would assume people with the kind of EDs your W has resent you for trying to help in the best of situations, and your marriage, pardon me for saying so, is not that. So now, you, the "quasi-husband/lover" has to try to use your leverage, which is dramatically undermined by the state of your marriage, to try to get her to save herself, or maybe even save her on your own. Monumental task. I'm sure it feels terrible.
What I can tell you Rob is that I have seen you struggle but in the end, make the right call most of the time. I am sure you will do so this time. I really feel for you and this post was not to try to make you feel worse about your sitch, just my attempt to summarize it and let you know that I understand, even though I don't really know what to tell you to do.
Keep posting and as usual, I know there are MANY people here who care about you that will try to help.
