So sorry that you and your kids are hurting. I was with my XAH for 25 years. He had periods of sobriety but no real recovery. I didn't know much about addiction when we married and he hid his history. I stayed much longer than I should have. At the end, he had been sober for 3 years when he relapsed cheated and left. He went to rehab again after that but it didn't stick. Even when he was sober, there were other things happening behind the scenes that I didn't know about. So often, they just transfer addictions. He was in and out of program for 20 years but never got honest or really did the work. So much lying and selfishness. I eventually went NC and divorced him.
I'm sure it's even harder with kids but they will also be a comfort. I never had them and I would have liked to feel that at least, something good came out of all those years. My ex had a son from another relationship but predictably, was never much of a father.
I know it doesn't seem like it now but you are still young enough to forge a different, happier future for yourself and your children. In a way, leaving is sometimes the only kindness they ever show us, although not intentional. Living with an addict is like balancing on a seesaw. You're always compensating for instability. I hope you find the strength to move forward and reclaim some peace. Best wishes.