Twofish, my heart and prayers go out for you and your children.
I am the mother of an addict too. For years I tried to help/fix/save my son, letting him turn my home into a war zone. He would find recovery and stick with it a while then inevitably relapse and the cycle would continue.
I became very sick over this, like you I lived in fear all day every day and it began to eat me alive.
What helped me, what literally saved my life, was to find meetings and go every week, and learn to work a 12 step program that has been the foundation of my recovery ever since.
Maybe see if there are meetings in your area, Al-anon seems to have more if there are no Nar-anon meetings. CoDA (Codependents Anonymous) was my home fellowship for years and is another similar fellowship that is about us finding out balance again and learning to live healthy lives.
Stick around, the sticky-posts at the top of this forum have a lot of helpful information, and know that you are among friends who understand.
Hugs