My ex was the same way...only I witnessed the abuse and mental unhinging...and just plain psychotic incidents. Others started to see it though...but I did keep a journal for years in case I ever needed it-and I did. I also took pictures of items he broke and threw during rages and discussed all with my therapist and the kids therapist as they witnessed some of his evil.
I would say document everything you can recall-and ask witnesses to write statements for you-to protect your children. My thought is if he's so far gone, it won't be long until he totally goes off the deep end or more than likely will not want to be involved in his kids lives (this from someone who's ex threatened continually while we were married and after divorce but has chosen to not be involved in his kids lives for more than two and a half years). They are a lot of talk....nothing more.
I was granted soberlink for my ex and he has failed so many tests they shut his device off and deactivated his account last year....push for soberlink...it's worth every penny!
I too was so nervous at the beginning, where you are now....but flash forward to the final divorce hearing and when my ex lost all rights to his kids two years ago? I was no longer afraid, I was strong and brave-and you will be too...just keep taking another step forward!
Please keep us updated!!!! Wishing you peace and strength...I remember his I felt at the time of temporary orders-it's hard but you can do it - stay strong for those kiddos!!