You are just incredible.
So patient with that awful man.
He wants 50/50 to avoid maintenance.
He doesn't pay his share and I really hope you are keeping a detailed list of all monies that he owes to date.
He also is making it difficult for you to work and provide for the children.
That has a whiff of Coercive Control, which is a crime.
Keep notes.
You may wish to talk to Women's aid about this at some point.
Limiting your ability to earn money is Coercive control and is a crime.
Read up on it.
It may be something that you will want to text him in the future and have on record.
He doesn't want to pay maintenance, he doesn't share costs and owes you money, you can name the figure, and he is making it difficult for you to work and provide for the children.
You can ask him what he suggests to resolve this.
Getting this down in a text could be very useful.
I repeat, you are amazing.
Your children are so lucky to have you.