Brake Pedal goes to floor

Well,I must have misunderstood; I thought the car needed multiple stabs to get the rear to work. It seems that was an error. Ok well that eliminates sloppy-loose slack adjusters then. Since the rears actually are doing all the work, obviously the fronts are not contributing. Since the rears are so touchy, and the pedal is low, this would seem to indicate that the rearmost piston has traveled all the way to the front, and is operating the rear brakes mechanically. When this happens, the compensating port for the front brakes, which is in the rearmost chamber gets blocked, and no more fluid can enter that line.
But additionally, you said the pedal hits the floor! These two situations can only occur simultaneously if the rear slack adjusters are in fact loose.So I would still start there. If you have a booster, there is supposed to be a big return spring in there which is supposed to push the pedal back up to its normally parked position.Without a booster,this job falls to the rear shoe-return springs. When they pull the shoes back, they force the fluid back up the line to the m/c and then thru the inter-chamber fluid, parks the pedal. Now with the front system failed, the inter-chamber fluid is not there so the pedal has no way of parking itself.
So now,I'm gonna argue that the non-parking pedal may be preventing the front brake system from working, due to the closed C-port.

So now if it was my car, I would clamp the front brake hoses, and if the pedal gets hard within a few strokes,by lifting the pedal back up to its parking spot with a toe under the pedal,then the air is upstream after the clamps. But if the pedal still won't park, I would redo the bench bleed, and bleed the front system somewhere else between the m/c and the clamps. If the pedal now gets hard, I would remove the clamps and proceed to the calipers. But if with the clamps on, AND the re-bench-bleed AND the re-bleed say at the flex-hoses, and the pedal still not hard, grudgingly I would replace the m/c.That's what I would do on my car with rubber flex-lines; But I would not tell you to clamp your lines on account of they say this can damage the lines internally and you might have a catastrophic failure at some future date. And on examination of how these lines are built, I can certainly see that. That's what people say.
But I tell you what, if you don't figure out some way to do this, you will probably have to replace the m/c. And if the new m/c makes no difference, then you are out the cash and no closer to solving the issue.
And I'll tell you one more thing; if you disconnect both steel lines from the m/c, bench-bleed it on the car, and then install plugs into the ports; A hard pedal now means the m/c is just fine. Conversely, a soft pedal now or a pedal that falls over time, guarantees the m/c is junk.