Thanks to all who took the time to respond. I'm so happy that all of us here at KH bond over our love of knitting, but are ready to assist a fellow "knitter in kneed" (I could not resist; so sorry!
After reading everyone's suggestions (here and on Ravelry; I made the same post there), I have decided to bring this up during my review, which should be coming in a few weeks. Human Resources is aware about the "badmouthing" and has spoken to him about it before. Clearly it has not worked.
I don't feel too comfortable confronting him on these issues because there are days I just cannot read him or his attitude. He will get himself into a tizzy if someone does not do something for him right away, but if I tell him I am taking a day off or leaving early and asking if it is okay, it's always "it's not a problem," "what I do is not important." And yet this is the same man who called my home on a day off, when he was told I had been out of the office (and incidentally, was out of the office the previous workday due to illness) - and then when my father offered to get in touch with me, suddenly it was no big deal! Thus, I have no idea what kind of reaction I would get - the wrath from high or nonchalance.
I am getting my house in order for a job search, but it is unrelated to this situation. In my post, I alluded to a temp position within the firm (librarian) related to my in-progress master's degree (library science). I was filling in for our librarian on maternity leave and I found out this week that she is coming back right after Fourth of July (three weeks early). The plan was that I would start looking for a job that could put some of the experience I gained in the library to good use - that plan has now been accelerated a bit.
I do have a bit of saving grace - after tomorrow, he is out of the office for the next three weeks on business and personal travel.
I'll be sure to let the forum know how all this has turned out.
Many, many thanks again.