I’m so sorry that you’re going through this, it sounds awful. I have this with my son, but it’s heroin, and have come to the conclusion that loved ones have little control or influence over what happens. It’s not their fault, if they could solve it right now I’m sure they would. No one chooses addiction. But you need to prioritise you and your children and get counselling around how you best do that and also not let it become a secret that prevents you from getting support from friends and family. Famanon and Drugsfam will also be able to help.
This forum is amazingly kind and supportive. Just knowing someone else understands what you’re going through makes this less lonely.