I've spoken with my head and an Ass. Dean, so I've got some course of (in)action to take. Because the harasser-in-question is leaving soon at some unknown date, it may be better to do nothing than to do something. This is the type of person who retaliates and retaliates big, so it is probably best to not respond to his emails. The only thing to do is to cooperate and be quieter. I'm very happy to attempt being quieter since it's only a temporary situation. I might even have my office hours in a conference room rather than an office to minimize problems. I'm mad as hell about the harassment but I want to be as cooperative as possible. If he continues to harass me, then I can at least point to my attempted cooperation.
Still, when I see him in the hall, he gives me withering looks. Today, I even ducked into a restroom to avoid interacting with him! I feel like I'm five years old again.
Strangely… he was really loud today in his office.