Welcome to Just Answer
I am a Solicitor and will assist you.
I note that you are trying through solicitors to agree arrangements but that your ex is still causing you problems.
You state that on Friday – he followed you and was driving erratically with your child in the car. I also note that you have received a threatening email today.
I consider that you do need to report his behaviour towards you to the police and you should also consider referring to social services about his driving with your child in the car.
You have to protect you children and I am getting the impression that your ex is controlling and aggressive. Children should not be exposed to such conflicts.
I think that you also need to contact your solicitor. If eh continues to cause problems for you and make threats then a non molestation order may be necessary.
It may also be the position that suspending contact is appropriate if his behaviour is escalating and this is placing your child at risk.
Let me know if I can help you further