That not the best way to connect a relay, if you can find one that is within the current rating of the output, connect it between the 5v and the output, the resistor should not be needed.
What is the 120v load you are disconnecting?
What is the function of the drive outputs? Drive alarm?
You do not necessarily need to shut the whole machine down, just disable power to the moving components plus use the drive disable input, if they have.