Tone controls simply bleed off treble by shunting the signal to ground through a capaitor. Just leave it out if you don't want it.

If all you want is a master volume control, run the 'hot' lead of each pup to the selector switch inputs. Connect the switch output to the volume pot terminal that the centre terminal is connected to when the pot is turned fully clockwise. Connect the centre terminal of the vlome pot to the 'hot' terminal of the jack. Connect the 'low' wires from the pups, and the remaining terminal of the pot, to the shield terminal of the jack.