what can I do to fix my spongy brake pedal

Start by pulling lines at master cylinder and plugging the M/C and basically 'bench bleed' in vehicle. IF you get a solid pedal from doing that , then hook lines back up and bleed the rest as you've done. IF the pedal does not get good , then suspect defective M/C.

Are the bleeder screws at the top of the calipers or the bottom?