First thing you need to do is check your mask and long hose and short hose (if your mask uses one) for a hole somewhere or incomplete attachment of the mask components.
Your leak line in its baseline is no where near 0.0 and it should be.
Not too long ago I had a similar issue with my hose and I couldn't feel it but I filled the long hose with water to see if it leaked or not and sure enough...it did leak but I could never feel the air leaking.
I don't understand what symptom you are having that makes you think you need lower EPAP. Can you explain in more detail please?
As for those centrals...that's really not a lot of centrals and I would bet some of them are arousal/awake related.
Go here and watch the videos and learn how to spot awake/arousal breathing being different from asleep breathing.
If you aren't asleep when something is flagged then it doesn't count except to make us wonder why someone isn't sleeping so great.
http://freecpapadvice.com/sleepyhead-free-software
By all means...give S mode a try and see if it does whatever it is you are wanting. You don't seem to need much pressure anyway.
Maybe try EPAP 3 and IPAP 7 and see what happens.
Next time you post your OSCAR report...omit the time at pressure graph and include the flow limitation graph instead which is a lot more useful.
First thing though.....take a close look at all your mask connections AND take the hose off and do the water in the hose test to check for leaks. That baseline leak is way to high at the pressures you are using. I would bet my last dollar there is a leak somewhere.
I may have to RISE but I refuse to SHINE.
