can a damaged cylinder stop stud (the small protrusion under the recoil shield), on a blued revolver, be successfully repaired or will this area, now, be always weak?
As I understand it, the stud is "riveted" into the frame and can be replaced. I doubt it's a job for anyone other than a well-tooled, experienced gunsmith.
The part you are talking about is called a "frame lug", and it's function is to stop rearward movement of the cylinder when ejecting cartridge cases.
It's replacement requires complete disassembly of the frame, and a pin punch and support block while driving it out. Installation requires a staking punch to set it into the frame.
This is well within the capability of an advanced amatuer hobbyist.