Mckell....honey!
As I read your post, I was thinking "narcissist," and then I was surprised to read your final statement, that "He is such a narcissist!"....I've dealt with such a person myself, and it took me a good three years of reading and research, help on a forum devoted to recovery from involvment with a narcissist, to get over it.
It seems you already know what you're dealing with regarding this man, your husband. If you have done much research on Narcissism, you probably already know that a true narcissist is not going to change, is all about ME, ME, Me, and cannot be helped, even if they express the desire to do so. Sorry for the negativity, but it sounds to me like you need to search for options for yourself and your own emotional well-being.
Your stepchildren are so fortunate to have YOU as the voice of balance and generosity in their lives.
Love
Patty