How can I be sure to get sole custody of my 6 year old son after he broke up with me, left me and my son homeless and is currently on pre-trial probation for domestic A&B against me. I just found out that he has been cheating on me and is currently with the same woman whose is on parole having been convicted (Federal) with a life sentence hanging over her head for a violent crime and has a very violent record. I do not want my son near her. What should I do or say to ensure myself and my son's safety at the hearing?

Like in any court, you need proof. Get documentation about her record, and if possible, some evidence that he and she are together. If you can afford a lawyer, get one.