Blessed-
I plan on this separation to be long term. If things don't go well, I expect him to drag his feet on the divorce process. Where I live, you can be divorced for abandonment after 12 months. I do plan on moving shortly after I put the house on the market, so in order to keep from being filed for abandonment, I need to file for a legal separation. It will also help me keep my finances secured (he's unemployed), so he will not be able to put me further in debt.
I'm also hopeful that he will not fight the separation, but he may fight a divorce. It's my quickest/easiest route to not living with him, basically. You're right, it's not that much different than divorce, but he doesn't know that.
bookwyrm-
You have to laugh about these things sometimes don't you? I'm actually becoming quite fond of what I'm calling my 'Plan B' - Me and DD having a peaceful happy life together. Doesn't that sound fun?