Wow. Sounds like your boss is really being a jerk. I was pretty lucky, because I was the boss, but my Board was very understanding and wonderful. (I was director of a small public library.). Isn't great, though, the way the kids and parents welcomed you! It's interesting that people, even though many of them are sympathetic and kind, don't understand the aftereffects of this horrible disease. They think, OK, you had surgery and treatments and now you should be all better. I know that I didn't know anything about oral cancer until I got it.
Hang in there, John, you can always vent here. We are all here for you!