His getting professional help does not guarantee that he will get better or that this will end
. That is his job, his alone, and not your responsibility. His GPs diagnosis of manic depression does not mean he is not an alcoholic too, they are not exclusive. GPs are generalists and not specialists. Treatment for the mental health issues will be very complicated because of the drinking, and giving up drink if you are addicted is extremely hard. If it was easy AA would not be such a booming organisation. If he says he can do it 'on his own' just take that and interpret it as, I don't want to give up beer and I have no intention of doing that. Addicts are very good manipulators and liars.
You need to put yourself first. Do nice things for you, follow your dreams and hopes, get out and about. Talk to people. Don't isolate. Tell people. Get financial independence, or information about how to support yourself - there is nothing wrong with knowing your options. CAB are good for that. And will have heard it all before. For the children, if you talk to the school, there is help and support there for them too. They will be affected by all of this.
Going to Al Anon family group meetings will help you understand how you can cope (or not) with his drinking. Going to CODA meetings will help you understand how to look after yourself. Both meetings will help you and also give you a lot of support, including how to not enable him, as well as meeting people with similar experiences. Also it will give you an insight of what it is like to grow up in an alcoholic and dysfunctional environment, it always frightens me the enormity of the effect of alcoholism on adult-children even after they have left the family home. You could try going to an open AA meeting, to better understand alcoholism, even ask questions.
Looking at the depression fallout chat room (google it) will put you in touch with people (many in the US, some UK) that live with partners with depression and manic depression, they are a lovely bunch. There is another website, the blackdogtribe that is worth looking at. If he threatens suicide take it seriously and call 999, don't suffer in silence. It gets to the stage where it is almost a form of manipulation... (if I didn't drink I would kill myself, if I can't treat myself to X I will....). BALDERDASH. And on the off chance if he does try to do this and you haven't told anyone you will suffer.
I would go to the GP and talk to them about your suffering and they may be able to prescribe some therapy or put you in touch with an organisation that can.
In my situation it was depression and drinking. He had access to the best therapy and help in the UK for years and went through the motions. Nothing really changed in his behaviour. I asked him to leave. I could not continue to live like that, it was making me extremely unwell, not to mention our children. For us there was no happy ending. Well, I feel this enormous sense of relief and excitement for my future, but realise it has to be without him.
I was watching some BBC show yesterday, talking about Addaction and a report they just came out with. 1/4 of children in the UK live with a family member who is an alcoholic and they are 7 times more likely to become alcoholics themselves.
. Completely pointless last paragraph from me, it just sat in my mind and made me feel sad.