I have been separated from my daughter's dad for 8 years now (she is 10). He was abusive to me in our relationship, primarily verbally abusive (shouty and sweary) with controlling elements - humiliating me in front of friends, calling me names, telling me I was fat (I was underweight at the time) blah blah blah. He also did things like hit walls, usually when I wasn't in the room but sometimes when I was. This wasn't all the time, it was on and off usually triggered by alcohol. He also sexually assaulted me in my sleep on more than one occasion (one main one, one where I stopped him before it got too far) and there was definitely also some barely consensual sex where I clearly did not want to and he went ahead anyway and I didn't stop him.
A while after we split up I allowed him access to my daughter one night a week, and this eventually increased to two nights per week when I started having counselling one night a week and needed childcare. He never showed any signs of being abusive towards my daughter and although he would barely communicate with me, she was happy with him and seemed cared for at his house.
Around five or six years ago he entered into a new relationship with an intelligent, competent, nice woman and their relationship seemed to be normal, albeit with him continuing his pattern of living a parasitic lifestyle (he refuses to work). I benefitted from being able to communicate with her on matters concerning my child and contact arrangements which was virtually impossible with my ex as he does not usually reply to my messages (or if he does it is a pulling teeth exercise) or take phone calls from me. This was a burden on her and did lead to occasional disagreements between the two of us.
Anyway, during the summer there has been an incident that has come to my attention in which he drunkenly verbally abused this woman and threatened to kill her in front of my daughter and the two younger children they have together. He never made any such threats during the course of our relationship but it doesn't entirely surprise me, although I would imagine they are hollow threats since it seems unlikely that his first act of physical violence would be murder. She had left the house and taken the children (including my daughter) to stay at a friend's house and called me to come and get my daughter. When I arrived she was also really drunk and I helped her get to her friend's house and made sure that she and her daughters were safe. She basically told me what had happened and also disclosed that he had also on multiple occasions raped her when she had been passed out. She also said that he is physically intimidating.
Since then, she has made him move out and he is working on himself apparently, not drinking and working through some kind of workbook for abusers. I have very little belief that he will change and am carrying a lot of shame that I didn't warn her, and also that I let him have access to my daughter, and she seems to be uncertain and still loves him. Since this happened (several weeks now) he has shown very little interest in contacting me to see our daughter, but has constantly been on her case trying to see her two kids (so I imagine it is more about her than about the children). Anyway, now school has started and normal routine has clearly not resumed I am not sure what I should do. Do I contact the school and tell them about all this in case he shows up at the school gates (I have no particular reason to think he would do so but I don't know), do I contact social services? I don't want to alienate his new (ex?) partner by doing so as our daughters are sisters. Everything just feels so up in the air and uncertain. My daughter has seen her father once since this happened under supervision of the new (ex?) partner but no doubt she will be wanting to see him again. It is very difficult to get her (my daughter) to open up about her feelings. She didn't seem particularly keen to see her dad after the incident but was happy when she did see him. Any advice or insight appreciated.