I can't give you a specific answer cause I don't use the software you have.. I'm also on a Mac which makes it even more difficult.
However, when I record in Cubase, the input level has to be adjusted from outside the computer using a Mixer. There's an incoming volume level in the system software and a choice between CD/Line/Mic but I always leave it to Line and at full volume.

In Cubase, I click 'monitor' in one of the faders, and adjust my external mixer until it peaks as high as possible.
Then I adjust the master volume so that the music mixes with the guitar.

Sorry it ain't much help, but you may need a way to control your guitar volume externally.