1a-c. have you changed your fuel flters?

2-3a. thats a vac leak... those can be a real pain to track down... i dont have the same a/c but as far as i know the vents are controlled by the vac system

4a. prob a contact issue in the switch in the steering wheel... mine has the same problem and i still have not fixed it yet

4c. the dash rehostat is prob the culprit... it is one of the knobs below the gauges

6. yes from the dealer but you will need your registration and they cost between 20-30 dollars

not too sure about the others but im sure other folks will chime in