I would like each of the TBX controls to control the bridge and the middle pickup separately. One specifically for the bridge and one specifically for the middle.
I'm presuming there will be no tone modifier then for the neck pickup.
Unsolder your existing two tone pots from the pickup selector switch and from their ground wires. Remove both tone pots entirely from the pickguard.
Install the TBX pots onto the pickguard. If they didn't come pre-wired, Solder them up as specified with their instructions and ground them with the existing wires from the tone pots but stop before wiring that last wire from each of them to the pickup selector switch.
We shall use this illustration as your guide:
Look at the pickup selector switch. Notice that it has 4 upper and 4 lower terminals.
On the lower half, you'll see one unused terminal. Solder your lower TBX's lead wire to that terminal. Next, solder your upper TBX's lead wire to the terminal immediately to the left of the one you just soldered the other TBX pot to. This will now leave the bottom left terminal unused. That's it, you're done.
Test and if all is well, button 'er up and enjoy!