Good finds
Brandybuck, now what Tolkien doing this for a purpose? Or did he just write it down unconsciously? With intertextuality it's hard to tell if he did it for a purpose, you got to know the author, and think, would he write something down like this in a story to serve a purpose? With metareferences it's a lot easier, if Tolkien used the same names that were used in the Nordic/German story, it would be a metareference, and there it's pretty easy to tell, that the author is using to serve as a purpose. Where intertextuality it's more difficult.
I could be wrong, but I'm almost positive in LOTR, and The Hobbit, Tolkien doesn't use metareferences.