So the exposed strands are not the actual cable but part of the reinforcement inside the black plastic tube? So is the black tube broken or is potentially nothing broken except the plastic ferrule?

That would be good news but where can you get a new ferrule? Or would a roll pin work? And obtaining one, is the only way to thread the cable through it via detaching the cable from the derailer?
Pls forgive my incorrect terminology, if possible.