I got good results with a CD that was badly etched with insect repellent by first washing well with cool soapy water, rinsing, then using small amounts of brasso on a microfibre cloth with mostly orbital and radial motion, followed by periodic water rinses for inspection to determine completion. Finally a dry buff with a clean cloth. It worked incredibly well as the etchings were at least 0.3 mm into the carbonate. Scratches should be a snap. I expect a suspension of 200 mesh or finer alumina in water would work as well as brasso. Patience is required. Practice on a junk or blank CD.
Cracks and bubbles you can't do much about that I'm aware of.