NBR: I hate my boss (long rant)

Okay, I'm a teacher, so when I say "boss" I mean "principal."  He is a military guy who kind of has taken to treating his employees like we are in the military.  My wife, who works for our organization at a level above him, calls him a bully.  He demands compliance and isn't very understanding, particularly via email.  He is slightly easier to talk to in person, but he's never around for that to happen.  And email is his preferred mode of communication--brusque, accusatory emails, generally.

So a couple of months ago I got in some trouble for not attending an after-school faculty meeting.  (Trouble defined as a text message that read:  "Is there a reason you were not at the meeting?  I require a detailed explanation.")  The meeting was on a topic I'd already been trained on and I expressed as such when I declined his email invitation, thinking it wouldn't be a problem.  Long story short, I was wrong.

 So now there is another meeting coming up on Monday, on a similar topic. Obviously, given the issue we had last time, I would plan to just suck it up and attend, but I've already requested (and he has approved) a personal day.  The personal day is because I will be attending my wife's boss's wedding out of town (again, wife works for same school system, but at a higher level.  So her boss is at an even higher level).  

So, now that this training has been scheduled, I'm worried he's going to take issue with me missing it, even though I'll be gone the whole day (not just skipping the meeting) and he already approved it.  I'm planning to talk to my direct supervisor, the assistant principal (who is MUCH easier to deal with, and someone I get along with really well) about it.  I'm debating whether I just stop with her and leave it at that, or go to him directly as well.  I just hate dealing with him right now, and even just thinking about having a conversation with him stresses me out.  (Not good for TTC either, obviously--I'm transferring to a different campus at the end of this school year for just that reason.)

 Thoughts, ladies?  Thanks for letting me vent!