Not sure what the others have said, but here's MY 2 cents.....
First of all, he's making a hostile work environment. No, he's not talking about you, but his frequent attacks (and that's what they are) are making it difficult for you to do your job. Y9ou might want to consider having all 4 of you sitting down to talk: The Head Director, you, him, and someone from Admin. Lay it out for the other two.
Secondly, involving the students in this conversation is an absolute NO-NO!!! THAT is something Admin needs to address. I'm kinda ambivalent about getting Boosters involved as they don't work for the school and you haven't mentioned anything about the students being hurt in any way.
Finally, STAND!! YOUR!! GROUND!!