As I noted in the edit to my comment in another sub-thread, their divorce happened before "no-fault" divorce was created. At that time, couples wishing to divorce would often concoct stories of abuse or adultery to give the courts grounds on which to grant their request.
It's doubtful anyone alive today could say definitively, but this could be an instance of that practice. I certainly hope it was.
I can't say I knew him well but I knew him out of school, and this is completely unlike the guy I knew. Your theory makes sense -- especially the humorous elaboration about thinking about calculus at all times as grounds for divorce -- THAT sounds like the classic sense of humor.
It's doubtful anyone alive today could say definitively, but this could be an instance of that practice. I certainly hope it was.