Past the ultimatum stage and need help with the next step

Hi all, I signed up here a few years ago, I think when I was on maternity leave with my daughter who is now 4.  My husband always jokes about his ADHD, but he truly has all the classic signs of it (that I see in my students at school who have been diagnosed - I'm a teacher) - gets obsessed with projects and loses touch with everything else, loses everything, quick to anger when he feels he's being criticized.  But he also has some amazing coping mechanisms that he's created himself, particularly where time is concerned.  He's amazing at using timers and his phone to keep him on time for everything.  And he works full time and is very good at his job.  So I had hope when I first approached him about us trying therapy or at least reading Melissa's book together that he'd be willing.  But he wasn't willing.  He felt if I was unhappy, then I had to fix the unhappiness myself because he was fine.

 I read the book and identified myself in the nagging parent role and slowly removed myself from it as much as I could (old habits die hard).  I went to therapy to get my thoughts together and the therapist gently suggested that if only one person was willing to work on the relationship, it most likely wouldn't work.  But the therapy also showed me something else.  What I had thought was just a "good `ole boy" drinking thing, was actually alcoholism.  Slowly, I opened my eyes to how much it was affecting our family.  I also realized it was preventing me from carrying out one of the suggestions in the book - to have my own life.  I was afraid to go out and leave my very young children with a husband who most nights of the week, drinks heavily.  I became aware of events I turned down and one that I actually cancelled when he'd had way too much to drink before I left.  Again, he was not willing to acknowledge that this was a problem or make any changes.

After a couple of years of dealing with some health problems that made it hard for me to make the big decision, I am finally here, recovered, but exhausted and no more spark left.  I'm definitely carrying the majority of the work at home and the child care while working full time.  This is after hiring a cleaning company to come in once every couple of weeks and asking my parents for help with the kids when I really need it.  Asking him to help in any way often leads to a "no", but if I'm struggling I get the old, "But you should just ask me for help."  I can't handle that anymore, it upsets me so much.  I've been asking him for years to stay at the table during dinner instead of leaving when he's finished but the kids are still eating.  But he won't.  He wolfs down his food and leaves.  Sometimes doesn't even come for dinner at the beginning.  He gets up later than the kids and I and then starts rushing all of us when he wants to leave.  Sometimes the lilttlest things like, "I think it might be garbage day tomorrow" turn into him feeling criticized and snapping at me about it.  I hate this walking on eggshells.

I've finally decided I'm done, but am worried about what a separation will do to my kids.  He's always rushing and snapping at them - when I'm really, really sick and can't get my parents to help with bedtime, it's awful.  He puts them to bed way too early, as quickly as he can and the crying is awful.  I'm worried about having to share custody in any way with him, both due to this and the alcohol problem.  He's fine to drop them off and pick them up from school (he does that now), take them to activities and maybe spend short amounts of time with them, but he can't handle anything that requires a sustained amount of time interacting with them.  And he's very against us separating - he's said it many times when I bring it up.  If I do go through with this, he is a game player, and he will try to make me pay.  I'm worried it will be by trying to get full custody of the kids by using the health problems I have had/still have.  

I'm so torn - on one hand, I can't see myself living like this much longer, on the other hand, I am really scared at what a separation might do to my kids.  Any insight, similar experiences or advice would be greatly appreciated!