It’s important to get the low pressure/master cylinder circuit working first. If there is air in this circuit the distribution valves will not open properly. With a master cylinder failure the distribution valves will still work but only with the brake pedal to the floor.
I would focus on the master cylinder circuit first. It is notoriously difficult to bleed. I use a vacuum pump on this circuit to suck the brake fluid through. Since the brake fluid is sucked out, a good seal is needed on the threads of the bleed screw otherwise you are just sucking air. I use teflon tape on the bleed screw thread, being careful to avoid getting the tape too low on the thread where it might come into contact with the tip of the bleed screw.
I’d get this circuit working first and see if it cures the problem you are having.