1990 Ford Mustang Hooked up jumper cables backwards

My father wasnt paying attention and hooked up jumper cables backwards while trying to start car. He noticed smoke coming from starter relay so he immediately shut off car. Upon further inspection he noticed one of the lead wires (blue) melted the copper wiring inside of the insulation. He spliced a new piece of wire in and no luck. The car will turn over, but will not fire. Ive replaced that relay, check spark at coil and distributor, checked coil, checked spark at plugs, checked fuses, and sprayed ether into throttle body and this thing still will not fire. What should I check next?