Is there any gcode that will home the machine with the limit switches mid job to make sure the machine still calibrated?
I’d imagine you can pass a $H, yes, but be wary of what this resets if you’re using Carbide Motion. This should only reset your machine zero, but CM might also reset your work offsets and lose you your Zero origin.
Is that a gcode or a MDI command?
It’s actually a GRBL command, but you could probably stream it in the middle of a bunch of gcode - the gcode is just a serial stream of characters pushed into the controller. Whether CM tolerates it or not, I don’t know. Really just need to try it.