Step children being exposed to violence in household, how can we help?

[LorettaLynn23]

My husband and I have been together for 5 years. There are three children to an ex wife ages 7, 11, and 14. We also share two children ages 2 and 4. The older three reside primarily with their mother, who also now has another child to a man she is no longer with. Long story short, his ex wife has a narcissistic character, possibly bipolar, and in every relationship it leads her to abusive behavior in front of the kids. She has introduced and moved her kids with 6 different men in the past 5 years, created a bond between them and her partners, and then the abuse would commence not long into the relationship. She throws objects, kicks, punches, slaps, pulls hair, screams and shoves, and corners her partners in plain view of the kids. This is the same behavior she displayed with my husband so many years ago in front of the kids. She tried to run him over with her car and purposely totaled both of their cars out of a fit of rage. He left her for the same reasons the others have. She was charged with 2nd degree assault once when she was 18, and now again last year her local police department charged her with assault following an incident between her and her former partner that her new son is to. The kids were in her custody during this altercation. He has since moved out and one month later she is now dating another man and has introduced the kids to him on several occasions. We know this is going to be the same outcome as those before, and do not want them hurt and are concerned for their safety. Every time we call CYS in her area, they do not take it seriously as she is very manipulative and puts on a very convincing act. She is only 5’ and weighs about 100 lbs if lucky... nobody would ever believe this woman to be as aggresive as she is. Especially around her children. To the public eye she is the most devoted compassionate mother, but behind closed doors she is a drunken abusive bitter soul who brainwashes her kids and exposes them to a highly unstable atmosphere. My question is, my husband and I are heading back to court to try and get custody of them. We hate to play hardball but don’t know what else to do other than to show that she is an unfit mother because.. well... she is. My step daughter (14) was actually my husband’s adoptive daughter, and she is aware of her mother’s behavior but tries to ignore it and indulge in her friends. She is not interested in moving because she is very involved with her peers. My step son (11) has been determined to live with his father since the day they separated. He has confronted his mother several times and she refuses, insinuating that we are coercing him and brainwashing him. The 7 year is thinks this violence is completely normal because that is all she knows. She laughs when her mom hits her boyfriends. My concern is that she will go in the court room and lie (because she will), and we will not have a convincing enough argument to get them out of that environment. Her charges are proof, we have more than enough tangible evidence to show her drinking and her multiple boyfriends, but I am worried it won’t be enough. I guess I am just looking for some calming advice. Any suggestions or shared experience would be appreciated.