Aside from the complex diagnostic situation, there is an important strategic consideration that I am not sure has been touched on here. When you get these symptoms at altitude, it is best to assume it is AMS until demonstrated otherwise. It looks like for at least one of you it may have been GI, but you don't guess about things like that on the mountain. So having had your experience, I would review it in light of the question: did I respond based on the assumption that it was AMS or in the hope it was something else?
PS: On the pack weight headache: I posted on this before my JMT last year. I had exactly the same deal on my training hikes with heavy pack. Finally concluded that it is due to exertion of a set of muscles around the base and back of the neck that are brought into play by weight carried on the shoulders. Solved it by a combination of hiking with a heavy pack to condition them, better adjustment of the hip harness and pack weight distribution. Probably the exercise was the most important.
