From my perspective as an ACoA (Adult Child of an Alcoholic), I think his walking out was a GIFT :day6, even if it doesn't feel like it right now.
You're doing great with going to Al-anon and your therapist. Working on you will help your family in the long run.
You're stronger than you give yourself credit for, and it's ok to be human. Give yourself breaks, often. Be gentle with yourself.
Don't worry so much about your AH. He'll either get:
Sobered up
Locked up
or
Covered up.
Peace,
skipper