He's not talking like someone ready to get sober.
My first marriage was for 13 years and there was no alcoholism involved. I would settle for nothing less than shared legal AND physical custody of my boys. She's the one that wanted out and I wanted 50/50 and to keep the house, she agreed and moved out. We lived close enough that they could ride the school bus home to Dads Mon-Wed-Fri and Moms Tues-Thurs, I dropped them off at her place Sat at 5pm. Sunday night was kids choice.
It actually worked out great. I got to see the boys every day, either did the morning routine or the evening routine, plus had time to myself, life was good. Maybe this would be a viable option for you at first, see how things go? Maybe agree to 50/50 physical custody only if you get 100% legal custody? If he blows it they'll end up with you anyway and you're already set with legal custody.
How old and how many?