I can't go into due to time right now, but it would help to do a frequency separation. That process separates the image into two parts (layers) with one being the colors and the other the texture. The texture looks fine except for the line that would exist between where the stained and unstained colors would be.
I don't have time to research it, but I believe this site from my bookmarks is how I started using this process. https://fstoppers.com …n-action-elena-jasic-3782
The places where there is on single color would be simple to fix. Background, black suit, white shirt. Just mask them off and convert just them to black and white. Then put the real work into the skin colors.