Heartbreak can happen no matter how solid we are in our sobriety. I'm glad you have a sponsor and are working the Steps. Al-Anon WILL help with the detachment. I've been married twice to alcoholics (before my own drinking became alcoholic) and it really helped me to realize that I didn't CAUSE their alcoholism, I couldn't CONTROL it, and I couldn't CURE it.
Detachment is a good tool for anyone to learn--think about working with newcomers who go back out. Same thing--you can't control, and aren't responsible for, their choices.
Keep taking good care of yourself. You also might want to check out (if you haven't already) our Friends and Family forum.