Dear stillswimmin,
You are far from alone, although I know how isolating having a BP husband can feel. 
I am so sorry for the pain you are going through, but in my opinion, you did the right thing by removing yourself and your children from a toxic environment. I'm sure it was not an easy decision, and one you were finally forced to take. Very familiar with young children 'triggering' bipolar reactions as my husband has the same triggers, and more...I have been with him for 13 yrs and we have 2 wonderful children, and I doubt 1 day goes by that I don't worry about what kind of mood he'll arrive home in, or how his episodes affect them, as I know they affect me deeply. I was wondering if your husband was on medications or seeing a dr/therapist? Mine is on meds and sees his psychiatrist once every 3 months, but he still has problems. His BP diagnosis came with a myriad of other disorders, the least of which is his sleep disorder and as a result, his serious lack of zzzzz's. I am a student nurse and have tried to absorb as much as humanly possible about this illness to try to help and support him, and at the same time minimize my own hurt, confusion, fears and disappointments. I've seen a therapist for years on/off to try to find the support and ear that I need to try to understand 'the bipolar mind' and get through the rough times.
I came very close to leaving my husband with our 2 children last year. I saw a divorce attorney and I was in a fog (likely the depression I was feeling at the time), even though I knew why I was doing it. I guess we've been together so long and I do love him, but I wonder sometimes when enough is enough.
Bipolar diagnosis is so different for each person. Many friends I have met on this board in the past manage it amazingly well for what they are suffering with. Some don't try at all, or they definetely don't have the awareness, and those that they love get hurt over and over again. Even someone suffering with BP would get tired of being hurt over and over again by someone they love.
It doesn't help that your ex is being so selfish and your children are suffering, as I know you are. I just hope that he realizes what he is doing sooner rather than later, but I'm not sure what state of mind he is in. Your children are lucky to have you, and I'm sure you will be the strong, unconditionally loving mother that they know. There's a reason to stay strong, ya know? But sometimes we need support and help too.
I'm here if you'd like to chat more...it's hard to talk about with those who don't really understand.
Prayers & hugs to you and your children,
4support