Hugs. You've got a lot on your plate. I think your questions are honest and good ones.
Getting sober will affect your relationship with your husband. No one can say how. I've been on this forum a long time and I've heard every sort of variety of outcome as far as marriages when one or both partners get sober. So don't count out the possibility that things could improve there.
I will say that as a mother of three myself, I think that trumps everything. Every other relationship or concern. Not only because of the deep love we have for our children but because of the real responsibility we have to do the best we can by them. Getting sober can only help your children. I do believe that is the priority.
I'm glad you are here, there are many people here with experiences similar to yours who can offer support, and all of us here are on the journey of recovery.
You can do this and it will be worth it.