How can I keep my ex from getting any sort of child custody?

My ex-husband abused my older children, he was arrested and indicted by a grand jury for multiple counts of rape and forced sexual assault. He never got convicted because just prior to trial my legally blind daughter whom was raped almost took her own life. We already had a report filed with the courts done by a professional child psychiatrist (guardian ad litem ordered by the courts) that found for me the mother in ever part and stated that she believed he had indeed committed all of the crimes he was accused of. Her recommendation was for NO CONTACT whatsoever, she also questioned his mental stability and he is now collecting SSDI under a mental disability. He has threatened to kill me and he insists he will get visitation. Help I am scared out of my mind, I live every day with the results of the abuse he has already caused, and my youngest child( the only minor) doesn't want to see him. She never bonded with him, and has not seen him in 7 years, she is 10 years old now.