Serge only had 2 OAs last night. Doing a range of 8-14 isn't going to help. The machine is going to detect flow limitations and try to treat them with more pressure. The thing is, I think any pressure over 9 likely isn't helping Serge since his airway is probably pinned as open as its going to get. The extra pressure won't do anything but cause discomfort and/or CAs. This is why I think Serge is better off with a fixed pressure.
Its possible that 9 with EPR 3 is as good as Serge is going to get with his current machine. That said, I think another day at 8 EPR 3 is probably worthwhile as an experiment, and if he gets the same result then try 9 EPR 3 for a week and see how it is.
I don't think he should lower his EPR to 2. His flow limitations would go up. He's in a tricky spot, but his big problem are the arousals/flow limitations and not the apneas. Hopefully the treatment emergent portion of his CAs subsides with a little time.
I was in a similar spot as Serge (but without the same amount of CAs) where increasing pressure didn't help to improve sleep quality and only caused me discomfort. What really helped me is when I got a VAuto, reduced my pressure and increased my pressure support to 4. My 95% flow limitations went down to zero at that point, and I was able to start getting decent sleep.
Edited to add: I completely agree that the less ramp the better (with zero ramp preferable). Capping the ramp at 15 minutes sounds like a good idea to me.