T.F.
In your situation, I would see a good dermatologist because your body has been through so much.
A dermatologist can give you a special crème with HQ that will bleach out dark spots. It is very drying to your skin.
I would think with your specific situation, you need something with more "punch" than OTC products in order to start seeing a difference. I do know Proactive has a product. My hubby is a golfer and will occasionally get dark spots and he uses the Proactive product for dark spots.
Personally, I use special essential oils by Kaplan MD and Clinique Repairwear Serum. The main thing I do is wear sunscreen DAILY without fail. I even put some on my hands and neck.
I hope you are in much better health now and will continue to improve.