Unless you have a Carbon Fiber frame, then I can't see how it is any different that painting a car. I wonder how much a local shop would charge for carbon blasting the frame. That way you have a nice clearn start. You could also then consider having it powerder coated again.

Otherwise clean with prep solve. Scatch up the surface with green scotch pads for paint adhesion. Fill the chips with thin body filler (putty). Then hit is with some high build primer. Sand, apply a sealer coat, and paint. It will be as good as new.

As far as the bottom bracket goes, I am no expert. The width is important to ensure that the crank lines up properly with the frame. You don't want the smallest cog hitting the frame, but you also don't want it too far away from the frame. Others will hopefully be able to give you more detailed information on how to measure this.

Happy riding,
André