Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Well, if it is loose, you have to remove it - sometimes you have to use force.
Later, you can make a new threaded bushing and solder it to the boiler. Another
option is to desolder the lid of the boiler and repair it from the inside. Anyway, you should be a good craftsman.... this is not easy peasy. You may also try to use heat on that drain cock.
I could do it for you but unfortunately I do not live around the corner.
Good luck, Arnold