I hope someone can point me in the right direction?

In the distribution block or proportioning valve there is a pressure switch that is installed between the front and rear systems. During bleeding the side being bled will be at a lower pressure which this switch sees as a leak and trips the light. Once the system is bled and the pressures equalize the light should go off.

Quick check to see if it's the pressure switch is to remove the wire from the connector on the block, if the light goes out then there is an issue in the block. If not then the parking brake switch or a short may be keeping the light on.

Regarding bleeding the master cylinder on the car; You can't effectively do it by trying to push all the air in the lines & MC out through the wheel bleeders IMHO. I would disconnect the lines at the MC and run short pieces (usually come with the MC) of line from the ports back into the reservoir and bleed the MC seperately.