Ignition Problems

I figured out my last problem, my cat is claugged. ive got another cat but i cant put it in til i get down to my dads cause he has a welder. well i know that the backpressure can burn a valve, so when my car starts shaking i pull over n give her a rest, then start it up and im fine. well 2 nights ago i pulled over, gave it a rest, went to start it again, and had nothing. i turn the key and the dash comes on like normal, but the motor wouldnt turn over. not even click. i have a b&m console shifter so i took the console apart and checked the nuetral safety wires. all was good there. spen 3 hours trying to get a tow home, the car only fits on a flat bed and no one would come out at 11 at night. but finally got someone. so sittin in my driveway ive fiddled around with the nuetral safety switch wires. they were fine, but if i touch the positive from the revers light switch to the negative of the starter, which is shorting the car out and isnt good at all, i can get the car to turn over. doing this overrides the key, if its in the on position the car will start if i touch the wires, even when the key isnt in the start position. i was thinkin starter solenoid maybe? and secondly this was my uncles car since it was new. he used the same key since 1990. well that key has a crack in it and it was going to break off inside the ignition anytime, so i got the other key from him. this key hasnt started the car in over 15 years. it took a few tries but eventually the key worked. when i had this problem i tried the old key also. could the new key have messed up my ignition switch? anyone have any ideas? your help is appreciated!

What year and engine?

1990 pontiac firebird bandit II. tbi 305, out of 92 camaro. same motor though