I do sense a deep connection between the two of you, although I don’t buy into the twin flames new age stuff.
Anyway, to take him back as things were feels toxic to me. I don’t see him taking responsibility for himself, on his own, any time soon. He’s not into changing. No motivation.
One idea is to put conditions on the relationship – require treatment, AA, counseling, etc. He might make some mistakes, but if you put the pressure on, it feels to me like you might have a chance. This could also be test to see how much he really values you and the kids. He will need firm and consistent pressure from you, maybe even regular drug tests.