Can I safely disable a three way fan switch to use for providing ground to remote three way box?
Since you posted the model numbers of the switches, now I can be specific.

Remote switch:


Unwrap the tape from the white.
Connect black terminal to black wire, white terminal to white wire, and the red wire to the yellow/red terminal of the remote switch.


Main dimmer:


Unwrap the tape from the white.
Connect all whites together, including the white wire on the dimmer.
Connect the red wire on the dimmer to the black wire going to the light.
Connect all remaining black wires together including the black wire on the dimmer. (Do not connect the black wire going to the light).
Connect the yellow/red wire on the dimmer to the red "traveler" going to the remote switch.
Cut and cap both ends of the red wire going to the light.