Usually when my eyelid twitches, it's usually related to smoking or drinking coffee - your DR that is treating your sleep apnea should have some input - perhaps you could ask to speak with them over the phone and get that answered quickly?
No I don't think you have air in your eye. I work with alot of people who wear them and I've never seen that. I think that when you fall asleep, it either sqeezing near your eye or rubbing, which is irritating your eyelid nerves. Maybe you could try to adjust the mask a little differently or track where you fall asleep and wake up to see if you are moving alot.
Yes their is a possibility of this thing. If you can remove that mask then try doing that and watch what happen to your eyes.