You know I also use max humidity setting of 8.
And I actually have times where I feel I could/would use more if I could.
So I get what you are going through except yours is worse. Mine isn't that bad (no cracked lips and only very minor and not common dry mouth which I am reasonably certain is mouth breathing dry mouth) but I have tried to imagine what I would do if I were in your shoes.
I am under the impression that the machine in manual humidity mode wants to dispense a set amount of moisturized air and the hose air temp does NOT change the moisture content.
BUT.....I am going to go out on a long skinny out there limb and muse out loud and think about how much moisture my nose is getting when the condensation happening is pulling moisture out of the air that is going to my nose.
The machine doesn't change what it wants to dispense based on hose air temp when in manual mode but I wonder if it is possible that once condensation happens we don't end up getting the amount dispensed because it fell out of the air and condensed.
Just a way out there thought. I was wondering what adding a room humidifier might do??????
Other thoughts....you really probably should do the tape thing for one night and rule out mouth leaking/breathing as the dry mouth cause.
Don't rely on leak graphs to tell you that you weren't mouth breathing/leaking and it doesn't take but a handful of minutes with mouth breathing to dry out the mouth really bad.
I have proof that mouth breathing doesn't always show up as a big leak on the leak graphs.
Here's an example below. I woke up one morning and I was mouth breathing so I decide to just continue mouth breathing and see what it looked like on the leak graph. It was a nice gentle mouth breathing....no massive exodus of air out the mouth or anything like that.
I circled the known awake mouth breathing time at the end of the night in red....that tiny leak was nothing especially when compared to earlier leaks.
at this time of the year, I would wake up with a bone dry nose every day and it soon would be screaming at me in the form of slight nose bleeds.