sorry, not much time today.
sleep cycle is a generalisation. it is not exact. When he's woken up by external things, like pain, it can happen.
Teething might cause EW, period. I am not saying that it is a problem that his lower bottom teeth are still not out yet but I thought usually they would come before the molars. Have you taken him to the dentist (usually not at that age) and perhaps the canines are blocking them and causing pain?
you have done some good observation there. I hope your plan works. Teething is tough, though. Gotta run. fx