I'd look at products like topaz photo ai. It should do things like color correction, brightness and sharpening. I don't think it does dusts spot / scratches although that's probably on the feature list to add. You could also use a two step process with another program for dust spots.
If topaz or similar ai product doesn't do exactly what you want, I'd start scanning but wait a year or two to process as these programs are rapidly improving.
Use internal drives with a dock and store cold. Saves the hassle of dealing with a bunch of cases and power adapters.
For fully on backup all the time use a versioned backup like time machine or a cloud service.