I was in that same boat...and I left a person who was "Mentally a child" . I liken his antics to Robin Williams. He's a very funny person. The down side is he's very irresponsible also. "Moron" or "idiot" jump to mind.. because he does things that defy logic, or explanation. My child is paying the price for me not choosing a better father figure for him.
Since I left him in 2003 (I stayed long enough for my son to be able to tell me when (not if) his father did something to him...) I have since reported him to CPS for child abuse, and a typical weekend at "Dad's" gives my son nighmares for the "Rated M for Mature" videogames he has my son participate in the day time. Games like "Half Life 2 " I suspect my ex husband does does that, because he knows my son will have nightmares when he's here at my home, and that his way of harrassing ME. It's my child shaken, crying and terrorized... I do call my ex to let him know it won't be tolerated, if he plays that game with my son again (crying child in the back ground) I will have his visitaton supervised. Other antics are, for the most part he does not call our son at bedtime like most "involved" dad's do, he only calls when it's going to be his weekenend-- if he's not cancelling ....and he rarely speaks to our son while confirming his visitation, drop off, etc with me. It's an exercise in futility, because if he does call during his "off time" it's to pick a fight with our son, in an attempt to get my child angry with me. Otherwise he avoids "his boy" entirely.
It's very, very good to get your child out of a full time situation with a jerk Rachel, but there is always "Visitation" hell. Dont be afraid to prosecute him if he does something harmful to your child. "Writting it down" in my state, does not mean a thing.
Protect your Kids. One "Mother Bear" , to another.