Since I take LOTR as entire, that is, I
need read nothing else to "understand" it, I am driven to say once again that I can only "deal" with it as it stands. I can't bring the Silmarillion in, or Tolkien's religious beliefs. I have to take Bombadil as he is: and to hell with everything else.
A work of art must stand on its own. What an author has to say about it is as suspect as anything said by anyone else. Tolkien was evidently a bit of a revisionist himself.
It may have been a mistake to "put" Bombadil in the tale. It might have made Tolkien's life easier, and might have made the tale more seamless, more "of a piece", to have edited him away. But art is tricky. The artist isn't always in control of his creation. The inexplicable happens, and lo! The tale must wrap itself around it and take it in, digest it, make it part of the body.
Don't get me wrong. I find all the discussion fascinating and revealing, and I'm impressed as all get out with the scholarship and thoughtfulness of my fellow LOTR fans.
But I read this tale forty years ago and read it again and again in isolation, so to speak, unaware of anything beyond the covers of my copies. I knew nothing of Tolkien, his education, his religious beliefs, the critics who thought LOTR was the greatest thing since sliced bread or the critics who thought it was a meaningless and not very good fairy tale. I'm not sure that learning any of that did me any good.
So, given that I knew nothing (and that I think it's fine to know nothing), how did I "explain" Bombadil to myself? Jeez. I explained him in light of my own reading and knowledge of myth and language and romance!!! What a sap. I'm as bad as the rest of you.