Sorry for your issue. If you test from the positive battery terminal to the negative do you have power?
Do you have grounds from the body to the frame, frame to engine, and engine to body? These are additional to the negative battery cable from the battery to the engine and fender.
The ground cable is obviously smoked. Change it and recheck for power.
If you have power at the battery and the negative is good, and no power inside car, check the distribution block on the radiator support for power to it and leaving it going into the car.
Start there and let us know what you find.