"1. Unreasonably happy. 2. Explosive anger."

That was exactly my experience. It was either extremely friendly and fun, or extreme anger. It was terrifying. I would usually stay up 24 hours in a row preparing for meetings because I would be too anxious not knowing what I was going to get.

>It was terrifying.

I feel this. I'd get butterflies knowing I had to call him or hearing the phone ring. I don't know how people like this remain employed for so long.

>I would usually stay up 24 hours

This is wild. Hopefully you never have to deal with someone like that again. Likewise, I would just leave if it ever got to the point of interfering with my mental health again.