"Also, I was thinking that if your body is concerned about bringing itself back down to a normal level (possible start of survival mode), does it stop sending oxygen to your stomach, thus possible nausea?"
For the most part, any nausea associated with AMS is caused by changes up in the brain, I'd say. It would be true, I think, that blood would be shunted away from the stomach, but I don't think that would be the cause, generally, so your reasoning about survival is logically correct....send the critical stuff to the "vital organs".
