I had a few hundred conversations with my XAH along these lines before I left him, with our then 3 year old son. He was like a case of arrested development, a 17 year old mentality in a 43 year old body. He never really matured beyond the onset of his addiction, and used 30 years of experience to hide it, protect it, keep it going.
After all of those broken promises about getting help, and finding out how far he would go to sustain his addiction, I quite literally fled for my sanity. I did not seek help, but did a lot of reading, and committed myself to my health and my son, and stepdaughter.
Since his precipitous downward spiral after I left and then his A girlfriend left, he had finally attracted the attention of his family, who spent 2 years and who knows how many thousands of dollars trying to save him. Only recently, 4th relapse since they got involved, did they finally go to Al anon to learn all I had, to save themselves. We are all quite close now.
This is his fight now. He lost his job 6weeks ago. Child support for his daughter is due next week, and if he doesn't pay he gets a bench warrant. He hasn't been heard from for 2 months. I have to say my life and the kids' lives are so much more peaceful since he is basically out of our lives.
His parents say that they struggle to do nothing, but vow no help unless its to recovery. They will not give him any more money. We hope he finds bottom someday, but its nothing to do with us. We get out of his way, and stay out of his way. And that distance gives us the opportunity to focus on ourselves.
And so it goes. May you smile with the sun in your face.