Oh No, Not Again!

[Tuor of Gondolin]

two words: "DON'T PANIC!" (at least until this May, when a certain movie is due out).
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One curious bit about Tom, which really argues against him being a Vala
or Eru is the observation about getting Tom to take the ring at The Council of Elrond (interestingly, made by Glorfindel, not Elrond or Gandalf):

...even if we could, soon or late the Lord of the Rings would learn of its hiding place and bend all his power towards it. Could that power be defied by Bombadil alone? I think not. I think that in the end, if all else is conquered, Bombadil will fail, Last as he was First; and then Night will come.

(Interesting, the capital letters in Last, First, and Night.

The theory of him being JRRT is interesting, and makes some sense, at least
as a partial answer.