Ulmus I will give you three contradictory pieces of advice , but hey, I'm an academic, its what I get paid for.

Seriously, the first piece of advice is to chill and not read too much into it. This might be a nothing and you wil have forgotten about it next month.
The second piece of advice, and unfortunately the more serious one, is to document every interaction you have had with this guy and the manager since the incident you described. Your post is an example of a contemperaneous record. Record times, dates and contents of meetings. Things llike petty retribution as in cleaning the bathroom. The fact you feel threatened and need to take leave. Tell a friend and a (trusted) co-worker this. If shit gets ugly, it will help you if you need to hire a lawyer if your work situation goes south. You shouldn't need to be looking for a new job. A good record should convince the boss of that.
Finally, there is the third piece of advice. If you honestly feel threatened, quit. Do it tommorrow. Screw the job. Its not worth getting shot over. I refer to suggestion number one, not blowing it out of proportion or letting us wind you up, but if you really feel this guy is a threat? Just walk away. Call a lawyer with what you've told us and you can probably score a severance package and a nice letter if what you've said is true. Seriously, evaluate the situation, talk it over with your wife, maybe call a lawyer and pay for an hour of his time and make the call. Going to work looking over your shoulder? Not ideal.

FQ13 who has no real wisdom. I'm pulling all of this out of my ass (except the lawyer bit) but sometimes it helps to think out loud and we are always here to listen.