I haven't seen the wiring, but I'm assuming the pickups are connected to individual volume pots, those are connected to the selector switch, and then the tone pot is connected to the selector. If that's right, you need to disconnect the tone from the switch, and connect it to the bridge pickup's volume control. You can find diagrams which won't be your exact guitar, but will show you how each part should be connected. A standard Les Paul diagram will show you how to connect the tone to your bridge volume. The selector will then connect directly to the output without being affected by the tone, and the tone will only affect your bridge pickup.
