2000 Ford Explorer Brakes, Very Low pedal

Last week I had a front passenger brake hose blow a half mile from home. I limped it home and saw the problem. Purchased a new hose, but it would not seal (after market Chinese made, different from OEM) at the caliper. I returned it and went to other local parts stores and they all sold the same, so went online and purchased one. I had planned to change the brakes soon anyway so I changed the front rotors, pads, calipers and both hoses. Bled the brakes and the pressure was low and pedal was so low car barely stopped. I went to bleed the back brakes, but could not get the bleeder screws to open and snapped one. Running short of time I replaced the back calipers and pads as well. Bled all four wheels, but still the pedal was very low and just barely stopped. Spoke with a mechanic and he suggested I changed the master cylinder as he had seen master cylinders blow after brake hose fail and fluid drains out. So, I changed the master cylinder with one from Advanced. Bench bled the master before putting it on, bled it on the car than bled the brakes again at every wheel. Brake pedal low, but car stops. Tried bleeding the brakes again with the car running and the pedal is soft but stops. What could be the problem/ My brother seems to think the master may be defective? With as much work and money I put into these brakes it should be stopping like new? Any suggestions? Thank You