C.O.
Sorry - but there is no severed ties. You have children together - your lives will be intertwined. Does this mean that you can't go to a soccer game or baseball game if they are at their dad's that weekend? I DON'T THINK SO!!!
Sounds like you guys would do great by having a family therapy. Getting past the anger and resentment and learning how to communicate and co-parent...you will have to co-parent together.
Tell him to grow up and realize that just because you are divorced doesn't mean your lives are not intertwined. It will happen until the day you die. Marriages, grand babies, graduation(s), life - it happens. He needs to get in touch with reality and realize there is no severing of ties. You have children together.