Hope - no apologies necessary. I think you might be right about your H's moods. It certainly could be the depression that is causing him to snap at you, etc. It could also be the old "you hurt the ones you love the most." I sometimes think that people act that way around those they are closest to b/c they believe that the love is unconditional. Maybe he feels like you are the only one who really accepts him, faults and all. I bet he isn't like that around ow...that would mess up the "fantasy."
I have said before that when my H and i first separated, it was definitely for the best. Things had gotten so tense b/w us, that it was unbearable to live in the same house. Granted, our separation in the beginning was a little different b/c it was a "therapeutic separation" but i do believe it helped our R. We were able to take a step back from each other to heal, without being faced with the other person every day. And, despite the dire straits of my M right now, i do feel, in some ways, that my H and I are closer...does that make sense? Its hard to explain, but there are certainly aspects of our R that are better. So, this separation, although horrible, could be for the best.