It looks like Jeffrey Epstein came in during the year that Donald Barr left, 1974, and stayed for two years after that.
Barr's departure, though, seems to have been so stormy and contentious that if Epstein had been his pet or pal, he would have had to leave as well.
Barr Sr. was a hard-@ss who suspended more than a few students, that, plus his age, may have been one reason why Hackley students shunned him.
The sex slave SF book does complicate the picture, but doesn't make it likely that Barr and Epstein were close.
Epstein didn't have a degree, but he had four or five years of college and may have gotten hired with school assuming that he would get the degree if he wanted a more permanent position.
It would be interesting to know more about the timeline. Noel Casler might have been just old enough to have known students who were at Hackley when Barr Sr. was, but the idea that Barr was some kind of sexual predator seems unlikely at his age.
Casler is aspires to be a comedian and that makes him exaggerate for effect.
I agree with your assessment about Barr Sr’s leaving the employment of the school.
As bitter as the ending seemed it would make sense that the school would not want to hire anyone that Barr Sr would have wanted on the school staff.
Usually if someone gets rid of someone they don’t want anyone like them or even possibly like them to be around.
A lot of writers dabbled in that type of writing for a while. It sold copy; not good copy, but it sold.
While I’m still fuming about no one (bad) has been charged yet, my beloved tells me I need to be patient. He says the American public expects all crime stories to be solved in 43 minutes. UGH.