Yeah, they didn't get to fly in the best conditions, but I still think I would rather have fought that way than in the trenches.
In my experiences, the faster the air hits you in the face, the harder it is to breath, no matter the altitude.
You have that right. I did a SkyDive this Sunday and free falling at 120 MPH from 14,000 ft, it was hard to breath. You sort of resist air rammed into your nose and you surely do not want your mouth open!
Yes they suffered and later had O2 tanks with them as others stated.
Also, combat did not last long at high altitudes, they quickly descended to much lower levels. Do to aircraft performance and pilot fatigue.