I think your first boundary is a great one! It will be hard at times because we become conditioned, and our line in the sand for that person just keeps getting pushed.
For myself, being involved in other things to keep me distracted helped immensely. I have two busy children, so that helped. However, I also joined groups, went to Celebrate Recovery, and reached out to family and friends. Not just for support, but also for accountability for myself. And I used the fine people here at SR for the same thing.
Big hugs, you are doing great!