Problems

My dads 2006 chevy ssr died on me today. I had to push it back home. The truck before it died lost horsepower it went from 400hp down to 350hp and that was it. I shot the throttle body with ether and it did what it was suppose to do it fired off and then it turned off. The two engine lights came on. The one was the engine light and the other one was loss of power light. I put my tester to the computer and got these codes. The codes are p0443, p0689, p1682, p2101, p2176, c0700, c0300, p0102, p0113, and 3-5 N/A code not sure what that means. The battery has been tested. It is good they could not test the alternator but they said since the battery is good so is the alternator. When this origanally happened I got codes The code P1682 ignition switch circuit could have been set from crqnking it without it starting and the battery voltage dropping too low. There is a bulletin for that code setting because of that condition. The P0300 is random missfire the P0443 is evap purge solenoid control circuit. The P0102 is mass air flow sensor performance. The P0102 can be caused by the same reason the P1682 can low battery voltage.I would have the battery tested make sure the alternator is charging properly also make sure the battery cables are clean and tight. Also have a back pressure test done to make sure you dont have a plugged cat. That could set a random missfire code the mass air flow code etc. Someone helped me with these codes on here. Any idea what may be happening. I think it is the throttle body. The dealer said it is the fuel filter that is why it lost horsepower. That is also all the other problems. They are trying to bull crap me. The truck fuel pressure is at 60 psi which is good. Thanks for any help.