Okay so what is the white stuff? paint form the wall you backed into, or the primer underneath? if it's the primer, it needs paint.

Well on the gas door, you'd be bondo'ing to rust, and that just doesn't work. If you removed all the rust you'd have a big hole.

The window area is hard to see in the pictures if the paint is actually faded or if the clear coat is just coming off. I'm sure you could do something to make it look better.