#1 Ensure your front calipers are on the correct sides. Bleeder nipples need to be on the top. They will never bleed all of the air out of them if they are on the wrong sides.
#2 Inside the Master cylinder there is a dual piston assembly and a proportioning valve. There might be an issue with inside there so you might want to see if you can install a known working one to test to see if your breaking response improves.