I am having a terrible time of it with OSCAR

Time to learn how to figure out awake/arousal flagged events from real asleep events.
Go here and watch all the videos. While it talks mainly about central/CA arousal flagged events...it can actually be any category event.
http://freecpapadvice.com/sleepyhead-free-software
The videos show you how to zoom in on the flow rate (which is your breathing breath by breath) and look for asleep breathing vs breathing that is irregular and you aren't asleep.
If you aren't asleep...whatever is flagged simply doesn't count. You have to be asleep for it to be a real sleep apnea event.

Watching now.

Takes a little bit of experience and sometimes we can't always tell for sure if we were awake or asleep but we can get a good general idea by looking at the flow rate.

About a month ago I had a night with the AHI 9.4....usually it runs 1 to 2.
So I looked closely and 90% of the flagged events were so obviously arousal related a blind man could see it. It was also a night where I just slept horribly due to back pain. Now I always have some back pain and a lot of tossing and turning and even the AHI nights of 1 to 2 are usually 75% arousal related flags. That really bad night I had done some things during the day that I shouldn't have...I over did it and paid for it with a lot more pain that night. So the high AHI night...from sleeping poorly because of the pain and a symptom of the poor sleep and not the cause of the poor sleep.

This is why I always ask the "how did you sleep" question when evaluating things. If we don't sleep so great then the AHI numbers maybe don't tell the whole story. When we have a high AHI because we were awake or half awake...the fix isn't more pressure...the fix is to try to fix the why we didn't sleep so great. In my case...quit doing stuff during the day that you know you will pay for with more back pain later.