When you drive the car and put your foot on the brake does it pull to one side? Or if you jack the front up and put you foot on the brake slightly and try and spin the wheels by hand do they apply evenly to both sides? As your o/s/f is connected to the n/s/r, and n/s/f to the o/s/r. If either is applying little or no effort on the brakes, bleed that brake and the opposite rear one. If still no joy the seal is gone in the master cylinder. also if you struggle to get fluid out of the nipple, master cylinder has gone. You could try a vacuum type bleeder, this may also help to get rid of any air in the system.

Make sure the rear brakes are set up by completely loosening the handbrake cable and winding out the rear shoes so they rub the drums very slightly after giving the drums a few taps with a hammer

The brake pedal will not be perfect until the frond discs/pads are bedded in.

That's what I would do anyway

Dan