I don't grow many paphs but I do not believe you are going to get much growth with 10% humidity. Is there any way you can set up a terrarium type area to increase the humidity to 40-60%?
The day/night temperature change is not really a 20% change as much as a 15-20 degree change. I would imagine if your plants are on a window sill you will get close to those changes in the fall.
Joann