Multiple problems Airbag, sensors,tires, check engine light, etc....

Within the first month after purchasing my brand new 2008 Aveo, I noticed the tire pressure light came on ALOT!!! Now @ almost 100k miles I have just changed the cam shaft sensor, timing belt, and serpentine belt. I have also gone through 5/6 sets of tires that wear wrong after multiple alignments. Now a week after the Check engine light is off it comes back on with a random misfires code...???? On top of all of that the airbag light has been on for almost a year now. I was told in order to find out why it's on I have to pay $80????? ARE YOU KIDDING ME??? then I'm supposed to pay to fix it on top of that. I feel like they are raping my wallet and REFUSE to pay that price when it takes less than 10 mins to put it on that machine to read the code. My husband has unplugged the sensors under the pass seat cuz that is where the problem seems to be I assume b/c the message by the clock used to work and does'nt work anymore to tell us if the airbag is on or off. He has re-plugged them back in and still the light doesn't go off even after driving it for 200 miles. Today I am having him unplug the battery to reset it for a half hour and hope it goes off then but im not hopeful. Someone please help me with my car issues....PLEASE????

Welcome to the site.

Lets break this down.

1) You have a check engine light with a code that reads random misfires. Do you have the exact code?
2) Your passenger side airbag light is on.
3) You go through tires very quickly.

Is that it, or did I miss something?