Oh i totally feel for you Kate, even 5 mins is distressing I can't imagine how you handled 2 hours!!! poor little guy!
As hard as it is to understand for us, it appears that it's totally normal and that they don't have any memories of that during their awake time, which is reinforced by teh fact that your ds is so happy and well behaved.
I'd suggest you to talk to him about how great it is that we get to go to sleep, buy him a safe friend for his crib and let him know friend is taking care of him during night time. I got a Precious Moments angel that says a little prayer if you press his tummy (some times ds rolls on to it so hard that you hear the prayer in the middle of the night...
it also has an off button if you'd like him to stay silent LOL), anyways tell him that friend is watching him through the night, or introduce a night light too so if he wakes at all he won't feak out.
I'm guessing that so many moves are making him for hard to get where he is at night, i mean he was used to wake in the middle of the night and probably go back to sleep without you noticing and without being awake 100%. Now when he does that, he finds himself in a different environment and has had that experience twice since April so that's why he's probably so confused and hard to settle.
I don't have much words of advice, but I've found that talk talk talk helps a lot for nightmares/night terrors. Somehow if you bring it to "real" (that is talking about it) helps a lot to get rid of it.
Another thing that many moms have seen is that lo's tend to get more nightmares/night terrors when overtired. You say your lo sleeps well during daytime but probably he's getting too tired because of the school so make sure he's resting enough and if you have any doubts, put him to bed 30 mis before his usual time. You might be surprised that it can magically solve his sleeps issues (crossing fingers).
Good luck! i hope this awful phase ends soon!