Chamber cast it if you really want to know about the chamber. It sounds like you got a very average lever gun job and are comparing it to a blueprinted rifle. The scratched up case with the pointed round looks like resizing marks from here.....
A cast will tell you what you have. The rusty threads are quite typical. One more bath to rinse the salts won't hurt it. Sounds like the trigger issue may be a case of talent fell shy of the sales pitch.
