HELP! I need advice!!! :(

Autumn • smoky mountain mama🌞
My stepfather has always been an atheist, and a violent alcoholic, with the most cursing you've ever heard a person curse. When i was young and a teenager, he only ever fought & hit me- not my mom or his children. there is NO reasoning with him, i could only hide from him- sometimes for weeks...
 I fell in love with Christ at 12, when i'd go to church with my neighbor.. and He has given me strength and peace to push through the abuse until i could afford to move out. Stepfather continued to drink and get violent with me until the day i left. Last year, i moved into my apartment with my fiancé and had a beautiful baby boy. 
Now my mother is constantly nagging me about him visiting my baby.. 
i let him meet my son when he was born. i let him come over one time a month after. but it hurt and made me sick. he's not kind, he curses the whole time...it just feels like the darkest toxic spirit is in the room.., 
I've told her that while i forgive him in my heart, i am NOT COMFORTABLE with him around my sweet, innocent baby boy.
I've opened up to her about it & told her to stop. 
How do i get her to leave me alone about it?