DD who is nearly 3.5, has come back from contact with her Dad (my ex-partner), very quiet and when asked her what kind of day she had with him she said "Naughty" and when asked to elaborate she ended up saying that Daddy headbutted her with an angry face because he was cross & he wanted her to stop the tantrum. Usually, when she lies or makes up stories she can't stop herself from smiling but she didn't do that at all this time.
She has in the past few weeks said things like that Daddy shouted at her until she stopped crying. That she doesn't like it when he does really bad shouting and that she didn't want to go to sleepovers with Daddy anymore.
Previously in the past he has had a period of only supervised contact with her around a year ago when she was 2, as she came back from contact with him absolutely traumatised doing strange monotonous screaming and he was crying as well when he dropped her to me in the morning. Then when he left & she calmed down she told me that he had whacked her and slapped her. Said because he was upset he needed to whack her. And said "Daddy cried as well".
Then she didn't want to go out anywhere and just wanted to stay in my bed with me, about 30 mins later she wet herself on purpose on my bed (she had been fully toilet trained for months no accidents since Day 2!) and then later when eating lunch at the table she wet herself again on purpose. She later said she never wants to go to Daddy's house again.
I reported to HV and SS. They said I had done the right thing to say only supervised contact. He was initially remorseful and admitted that he had been rough with her but said he never struck her. He did say he wasn't coping with having her 2 nights a week. But as soon as I reported to SS he changed his story and denied it saying what he did was normal parenting and that I was making it up/putting words in her mouth to punish him. (no motive for this as I left him & it actually made my life so much harder to stop the overnight contact etc).
SS then lost interest because he spoke to them and they said it didn't meet their threshold, due to no bruises and said that we have to sort it out ourselves or in court. This made me feel powerless really & in mediation he then bullied me a bit into agreeing to unsupervised contact again by threatening court, and just continuously minimising my concerns as if they were just me being anxious and ridiculous.
Fast forward a year and he made all the right moves ie. going to anger management as I had asked him to in mediation (I said DV perp course but he just did anger management) and turning into Mr Nice Guy so eventually I started to trust him a bit again and tried overnights again on his own, only for DD to start having night terrors every night & his behaviour to switch back again to controlling, nasty, harassing, hostile in handovers etc when he wasn't getting what he wanted which was shared care of DD.
He is now pursuing this through the courts as he has moved closer to us on purpose to do this even when his girfriend, work, family, friends everything is 100 miles away. As soon as he moved he turned controlling and hostile again. I don't have contact with him directly anymore except email and he texts me & my parents handle handovers for now.
He was abusive in the relationship with me - verbally, physically, emotionally, psychologically and I think he has undiagnosed mental health issues and definitely cannabis addiction issues too.
Currently she goes to him mid-week and alternate weekends, with no overnights, but I want to stop contact completely because of what DD has said now, and considering his behaviour has become more erratic...and let the courts decide...but I don't want to be accused again of "making it up" or "putting words in her mouth" as I know this will be his defense or to attack me verbally or through the courts, make stuff up about me etc - I know he will allege I can't cope, that I am the one with mental health issues etc, as is his style of defense.
I don't want the same thing to happen again where I let SS's lack of interest or my feeling that I don't have power to take him to court etc...stop me from protecting my daughter.
Another thing she said today is that she wants me to tell everybody and asked me to "protect" her. This is quite a grown up concept for her but she is really crazily intelligent/emotionally intelligent - has very advanced speech and memory & always has done - at 1 year old she had around 20 words and before 18 months old she was saying 4-word sentences and counting to 10! And she said again that she doesn't want to go to Daddy anymore as he frightened her. 
Any advice?? 