Who knows. It could have been slightly crumpled like that before November 22nd.
Yes. The Rowley report (CD80) mentions that SA Gies, who was responsible for the care and maintenance for the car, thought the damage to the windshield frame was done earlier at the Lincoln dealer on November 1,
1961. (the year must be a typo, but that is what the report says). Gies said that they were making repairs to the crank that secures the convertible top and damage may have occurred then. So maybe that damaged the mirror.
The story seems rather implausible as it means that not a single person noticed the damage to the frame. A photo of the car taken at Love Field on 22Nov63 shows no sign of damage there:
although the windshield upper frame is partially blocked by the roof support. However, damage should still have been visible if it existed then as it is in the upper part of the frame that is visible in the Love Field photo: