I want to message my abusers current gf
Why do you want to message your abuser's girlfriend?
I'm going to send her this message to warn her.
Normally it is not good to interfere in a relationship but it is okay in this instance. You need to warn her before she gets hurt.
Look I told you my reasons and I didn't mean any harm. It's fine if she has a bad impression of me.
You did the right thing and she will hopefully take to heart your warning. You should make sure to report his past abuse of you to the authorities so it goes on his permanent record.