Abusive ex wants name change for DD

[bananahammok]

DD father wants to double barrel and add a middle name.
DD turned 3 last week and father has not been a part of our DD's life, not present during pregnancy due to his own choice.
Then there was a non mol in place when DD was 6 months. Lasted 18 months and I requested it to be dismissed as I felt enough time had lapsed for him to not act crazy.
As soon as I had it dismissed he filed for full custody and is now taking me to court.
In the beginning, the week DD was born, I had already chosen name and said he could choose middle and double barrel surname. He refused and said "over my dead body". He refuses to call DD by her name and uses different name publicly. 3yrs later he now is filing for a name change and initially wanted name changed but CAFCASS didn't support. So now he wants middle and double barrel. I think it's too late and don't want this to happen. Has anyone had this experience? What was the outcome?

I don't know about younger children but my partner had to wait to be 18 to add a maiden name as middle name via depot. There might be a method for infants but not sure.
I found a problem with my name as an adult. There was a typo on the register and I had to provide documented proof of my spelling from before I was 1. Medical records were suggested to me as the best place to get this evidence

Count this as a life lesson.... unreasonable people rarely stop being unreasonable