Welcome. First, self educate and find out what the terms mean from your sleep study. Most significant was the oxygen desaturation issue. This causes organ damage; heart, brain, etc. Second, get in charge of your own therapy. If the mask you are using precludes you from getting good sleep, try a different mask and experiment to find the right size. Don't let this issue sit in the hands of a sleep tech at your durable medical equipment provider. Some masks are more appropriate for certain pressure settings than others. The question of muscle degeneration and apnea? That is a question for your doctors as it isn't one that regularly comes up on a forum like this. Low oxygen can't be good for your system as a whole though.
A very brief summary of the data you have posted: you have severe OSA but, on the up side, your lungs work well. To address some of your questions:
1) In short, no. Restlessness and discomfort do not cause OSA. The OSA recorded on your study is a chronic condition and happens whenever you sleep. There is a small but significant proportion of people who have OSA but are asymptomatic. That is to say that they subjectively rate their sleep as good and they don't feel tired during the day. No one knows why this happens, but it it is well described. Unfortunately, it also doesn't change the fact that severe OSA is causing damage to your body every day (or, rather, night).
2) 10 days is still very early. It often takes a while to get everything sorted and to begin settling in to treatment. WiredGeorge is right about making sure you have the best mask. If nasal has been an improvement how about intra-nasal (up the nose)? Investigate the options.
3) It is quite possible that OSA could exacerbate your muscular degeneration. It certainbly won't help.
4) Err... CPAP *is * the treatment. In fact, it's the only reliably effective treatment for the vast majority of people. It is not a CURE as the OSA is still there if you stop using it, but it certainly is a treatment.
It may not be glamorous, and it may take some time and work before you are sleeping well with it, but CPAP will definitely have a positive impact on your health, especially given the severity of your OSA and your muscular condition. It is worth the effort, so keep working at it.
Should have mentioned earlier that the wires that are hung on you and the grease they use don't make for a comfy sleep environment for anyone. Also, when they stick the mask on you for the first time, it was a super bulky mask and I certainly didn't feel comfortable but managed to sleep soundly for the first time in many years; probably because I had no or low apnea incidents after the pressure was cranked up properly for my airways to stay open. Going to sleep I was worried that I would have to get up during the night with all the wires and mask, etc. as I usually had gotten up a half dozen times for potty walks... didn't happen and hasn't happened since I started therapy. I just wasn't sleeping deeply. I didn't really think I had much of a problem as I felt fine during the day except for nodding off while riding a motorcycle or using power tools. That, of course, I understood to be kind of sketchy.