Every word you typed is almost my story to a "T". I am also in the mists of a whirlwind of erratic behaviors and the up and down drama of "I love you" and then horrible comments laden with guilt directed towards me. The co-dependent attitude of "I must have you in my life" or "your my everything" that leads into endless arguments of nothing more than me not giving him everything he wants, is beyond exhausting!
The fact that your husband is able to grasp that he has this behavior and is actively approaching it, does speak of his ability to at least try to do something about it. I think that in these situations, we have to ask ourselves why we have attached a person like this to our lives. Is there a reason or meaning for being a part of this journey?
I am facing this situation with much question and (trying to have) reasonable understanding but with my history of depression and emotional abuse, I ask if I am repeating old behaviors? I have spiraled into a depression of my own with the daily thought of suicide to end the pain of life. He seems to flip his switch when he sees the pain that he is causing and this brings in a new sense of "protection" into the game and that gives him meaning. I believe the negative drama and attention draws a inward sense of "I am needed" to the relationship, hence the co-dependent behavioral cycle that continues. Breaking this cycle of "I feel needed" is the hardest thing you can do with people like this. Since I am not emotional stable, I think we continue to feed into each other creating a typhoon of emotion and drama that goes round and round.
The only way that you or I or anyone for that matter and combat this, is to find ourselves outside of another person. How to do this? I wish I knew, but I believe the strength we get from our battles eventually brings one to a greater sense of self in the long run. Value yourself and others will have no choice but to find value in you.