problem bleeding back brakes

I flat do NOT BELIEVE in "vacuum bleeding." ESPECIALLY in the case of "cups" in drum brakes or hydralic clutch slaves, air can suck past the cup---simply because of it's shape. A cup in a hydraulic slave, or a wheel cylinder, is designed to hold POSITIVE PRESSURE IN (internal pressure), and NOT keep positive pressure OUT (atmospheric pressure), which is what you create when you pull a vacuum.

I also agree --one step at a time.

Stuck proportioning valve, or if you have a "factory" type multi block with warning light switch, it may be stuck or mis - plumbed.

Blow/ flush out the lines. If you blow them out, do NOT use your compressor, which contains moisture. Get something dry, like CO2 or Nitrogen.

Don't be afraid to crack fittings on the way back, such as at the prop. valve/ switch block. You need to be thinking of getting a friend who can pump and hold some pressure at the pedal, or else go to pressure bleeding (pressurize the master)

Make sure the master has not lost prime. It's why you have to "bench bleed" a master.