elves lover

I just finished reading Silm and who the f is Tom Bombadil, Goldberry, and who created the Hobbits?!?!?!?!?

I had theory that mayby Yavanna created Tom and the Hobbits but then how Ents didn't know Hobbits if they were created by the same person?

And why Tom Bombadil called himself the Eldest if elves were called Firstborn? If he was older than elves then only Eru could created him because he doesn't allowed Yavanna and Aulë to made their creatures (dwarfs and ents) the first livings on Arda.

I thought that Goldberry is conected to Ulmo or maybe she is daughter of Ossë and Uinen? That would make sense because she was the river-daughter.

Or maybe she is the river Sirion or other river that dissapered in War of Wrath.