Child custody/support

We did our own separation agreement before we got divorced. It says that I have physical custody of our son, how much he pays in child support and joint legal decisions to both of us. I had it notarized and filed at the courthouse. He sends me an email that says he wants to change visitation to 50/50 and no child support or he will take me to court and file for full custody. He has already changed the visitation without my consent and our son does not like this new schedule either. Does he have the right to change the visitation schedule? If not, how do I enforce the fact that I have physical custody of our son and he should go to court to get it changed. I told him that I don’t want to change things, but he did it regardless. He even stopped paying child support. So now our son is being shuffled between 2 houses for 3 and half days each.

He may file an action to have custody determined by the courts, but will have to show why the schedule in the Agreement is no longer appropriate and in the child’s best interest.
I suggest you contact Child Support Enforcement regarding child support.