Marvin, I’m sorry for your loss.
On that faint note, can you duplicate, say 4x, and use multiply on the top three layers? Then merge, then take a look at brightness/contrast if necessary.
there is also fade correction, which I have been using more often lately.
Ditto on the selection tools question! grrr! I keep getting the “refine brush” or “refine” something when I’m using the thing that looks like a crop tool, and refine must be a euphemism for “feather”, because it makes the outside single pixel half transparent. Which is fine, but I’m working on PATTERNS and they don’t repeat when the fill is used. I can’t turn it off unless I do it every single time.