Bilbo is Frodo's second cousin once removed, but since they're so close I think people refer to them as uncle and nephew because it makes it easier and explains the strong familial ties. I think even Bilbo and Frodo refer to the other as uncle or nephew in the books
Yeah that's correct. Also, can you accept Ringwraiths for Nazgul? And Celebrimbor didn't craft all the rings of power and I wouldn't call "Flame of the West" its English name, rather just its translation.