Wow! I wish I could answer your questions. I am using an AirSense10 since Feb. 2015, and really like it. I have used a CPAP machine since March of 2005 and this is the best one so far. Initially, my target pressure was 7 with a range above and below that. I don't mind the ramp up as it is only seconds usually. I log my scores from each night to see how I am doing and to watch for changes that might indicate an adjustment is necessary. When I saw my average number of sleep interruptions per night going up, the store I get my supplies from checked my records and saw I needed a higher average pressure. I had to go to the sleep clinic and they adjusted my machine for me. My average sleep interruptions dropped back to what is a normal range for me. I asked why the interruptions went up and was told it is because my throat tissue sag more as I get older. I asked if there were any exercises I could do to strengthen them and was told there weren't any.
When I log my scores, I enter all the data for each night, then log the number of sleep interruptions and the score on different sheets. My most frequent score is 100, followed by 99, 98, 97 etc. My most frequent interruptions per hour is .5 followed by .2 I have gotten 0 14 times. so far. I recently noted that when I got through with a big project, my sleep quality improved--fewer interruptions and higher scores--like 100 seven nights in a row and two nights with 0 sleep interruptions. I didn't realize there might be a correlation between stress and sleep quality.
I fall asleep easily, often within seconds, and am never fighting the machine. I pull the sheet and blanket over my head to keep all the machine air from bothering my wife. But, my weight is stable, so my issues are very different from yours. I easily sleep 7 or more hours/night without having to get up.
My current nose mask is an AIRFIT N20 Med sys - Amer and is the most comfortable mask I have had. No strap marks, no nose creases or skin breaking down.
I hope someone else with more specific knowledge on adjustments, etc. can answer your questions.
I do other things to stay healthy overall. Due to arthritis "everywhere", I take a water aerobics class at least twice a week, followed by light weight lifting to maintain strength. I weigh myself each time I am at the fitness club and maintain a fairly healthy weight. I never get down to my target weight, but am never more than 10 lbs over it either. The only thing that changes as it fluctuates is my stomach size. I have had 4 serious medical situations, each of which was correctable and a one-time operation or treatment as the answer, so I don't take good health for granted and do what I can to take care of myself. So far, it seems to be working. That doesn't mean I am home-free, but I do what I can and research shows to be effective in contributing to good health.
Good luck to you!