The battery drained and the car will not crank when jumped?

All lights on dash work, key fob works. It doesn't appear to be in anti-theft mode. At first all the dash lights stayed on after removing the key from dash. Then only the brake and battery lights glowed dimly along with the radio. All fuses are good, not sure about battery fuse but assuming good because dash lights work. Could the brake switch be faulty or the start button? Any direction would be greatly appreciated. The battery connections were loose, and the positive connector is split in half so to make a connection I drove a screw through the side and into the lead battery terminal. It is a good connection but I'm not sure if it's enough to carry the amps to turn the starter. I know it needs to be replaced but it's not my car.