Hi,
Sorry for my wall of text, I misunderstood the original instructions about joining For and Dcm, I didn't think you meant with mach 3 connected.
I can confirm that connecting these two and starting the toolpath does bring the spindle to life, disconnecting the two while the spindle is running stops it, and simply pressing the spindle off via mach3 slows it(but doesn't stop it fully) to about 70rpm.