Fun! I don't remember "Amon Lanc" at all, or Khamul being the leader.Couple of suggestions - "Angband" missing an "n". In #8, it should say "former realm of #7." In #10, it should say "former name of #9."
I agree. There were only three Silmarils, and their fates are accurately described in the quiz, so where would the Arkenstone come into it? It was mined by the dwarves, the Heart of the Mountain, not an elf-made Silmaril.
Not trying to argue but the Arkenstone make Thorin really greedy much like the silmarils did to elves like Thingol so it could be the silmaril in the earth held by Maedhros. However the Hobbit does not tie into the Quenta Silmarillion lore very well so I can't really say anything for sure.
While the Arkenstone as a Silmaril is an interesting theory, it would have been INSTANTLY recognized by Gandalf, Thranduil, and anyone else who saw it and knew anything about Middle-Earth history.
Some interesting reading though
http://askmiddlearth.tumblr.com/post/41497309376/was-the-arkenstone-a-silmaril