as you have to wire the volumes together, its easiest to follow the les paul wiring diagram, as that has VVTT.
To stop buzzing, you just need to ensure that everything is grounded, and shield paint/copper tape for the cavity helps.
With regards to loss of volume and tone. When you have both pickup volumes full, altering the tone pot for one of the pickups will affect both pickups, ie, will remove treble from your overall sound, not the specific pickup.
Heres a wiring diagram for you. Ignore the switch, and wire the two volume output lugs to eachother, then one wire from it to the jack.