What's the problem here, with the A/C and the idling engine?

2000 Ford Contour SE.
1. A/c blows the air out from the defrost vents by the windshield instead of the vents on the panel…

2. When I'm stopped at a red light with car idling, the car starts vibrating as if it wants to shut off. I was told the problem was a sensor that's connected to the engine that keeps the engine revved at a steady pace while it's idle. Is that true?

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