OP- So sorry to hear.
I have watched my husband go downhill over the past several years, changing into a bitter angery person as well. Its not as continuous as your wife's appears to be from your description, but it is heartbreaking and has literally ruined my life.
He projects his mood on me as the source. The WORST is: he agreed to treatment, tried it, got not the best care, and has relapsed. Now after having hope, I am losing hope again.
If you can get your wife to seek treatment, I just want to tell you, as others have told me: its still a lifelong thing. It wont be a fix, even if meds work. You are looking at a long recovery. If it can happen.
I dont want to reduce your hope, just know that you are not alone, and also that if your wife wont see someone, there really is nothing YOU can do about that.
What I have realized is that I feel a whole lot better if I tell myself I will work on an exit strategy. I suggest you do the same. and dont feel conflicted about it. Make your best effort to get her to see she needs help, and extend the offer to get help yourself so she sees everyone is in this together. Try to get her to see that the damaging things she is saying to your daughter as in fact doing permanent damage- and does she really want that?
Meanwhile, look into divorce, alimony, custody issues ON YOUR OWN and TELL HER NOTHING. Dont even hint at it. It does not matter that she is asking for a divorce, you do NOT tell her you are considering it yourself. I normally am a proponent of total honesty, but this is an exceptionally charged situation, so it would do no good.
What I am getting at is: I think you will now need to live two realities One in which this can be worked out, and one in which it cant. And put forth sincere efforts in both directions.
If I had your financial means, and could live separately from my husband, I would totally do it. I just dont have the means. And therefore I have motviation to give this a real try. I do also love my husband very much, but he has destroyed my trust in him with his awful behavior, which he at times completely defends, other times acknowledges and feels remorseful for.
Its really crazy living this way. I worry about my health.
Im so sorry OP. Your task is enormous. I understand what PP is trying to say about how its not your wifes fault if she has an imbalance, but it IS her fault if SHE CHOSES to BULLY and VERBALLY ABUSE the family and expect them to put up with it.
Then again, she is asking for divorce. Maybe in some distorted way she is trying to remover HERself? She is hoping the problem will not follow her? I doubt she is confident in that. Which would only make her more "crazy" feeling.
I never imagine my marriage would be marred by mental illness, but it is. And its truly tragic. I wish it was not.
DEFinitely talk to someone yourself, just to give yourself that space to vent and come up with strategies. I would say that is step one. Protect YOUR sanity. You will need it.