Hey Dave,
I assume you mean you press the zero button for these axes, not home. Okay, then you have the numbers. Do you have some example numbers after zeroing workpiece?
That would not have been necessary. With a (now earthed) spindle (in contrast to double-insulated hand router) you don’t need the magnet probe anymore. You only need one wire on the touch probe, because the spindle is already earthed. If the touch probe still did not work after switching to a spindle, all you would have had to do was swap the wires because some touch probes are wired the other way around (see here for details). The touch probe works perfectly with a spindle this way.
As Chris @ChrisM already mentioned above, using the 3-Axis Touch probe gives you more positioning repeatability than stall homing, either on a fixed block or jig, or at the workpiece itself.