Serpentine Belt

So I have a 2000 Dodge Durango and I had just gotten it up and running again after some repairs irrelevant to this but I got it down the road and it was driving fine for about 20 minutes and then the vehicle started to overheat well I figure this has happened before I’ll just wait for it to cool down turn back on and drive till I can get to the nearest gas station (less than half a mile)… as soon as I hit that off ramp I started smelling burning rubber and thinking it was my brakes trying to lock up because my abs and brake light were on I hurried up and pulled into the gas station. Come to find out my tensioner broke and the serpentine belt was rubbing on my alternator and tensioner arm. I got it fixed a couple days later no problem but when I started it up, it was shifting really at random rpm levels. Low, high, it didn’t matter. The more I ran it, it started to backfire if I tried to speed up, it would shoot up to 5 thousand, backfire, let off gas and it would shift. And if I stopped the engine, it eventually would turn of completely.