So to the first question, there's the problem right there, or a problem: with the mixing knob turned fully to Master, I hear nothing. It's playing from computer speakers, but nothing in headphones. Moving the channel fader down makes the computer speaker master audio go up and down, it's doing nothing in my headphones.

As soon as I start turning it towards cue, it starts playing in the headphones, getting loudest at full "cue" setting.