I notice in your profile, you say you aren't using a humidifier. Maybe for your dry mouth, you might consider using just a little humidity.
Hang in there and someone will be along with more suggestions.
I have the same mask; and my pressure sometimes hits 19.
There is a thread somewhere on how to fit the Mirage Quattro. It can be done.
Some might recommend a mask liner -- sort of a gasket between mask seal and face.
I've never tried it. Some people say it's their solution to leaks.
You are diabetic; and that may account for some of your dry mouth.
If you are breathing through your mouth, that will also cause dry mouth -- even with a humidifier.
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