At Tom Bombadil's House...

[The Half-Hobbit]

Many questions...lets see here. I believe that Frodo's dream is a vision of Gandalf on the tower of Isengard. It is a bit late though, as by that time Gandalf had already escaped.
Why is Bombadil not affected by the Ring? Not a clear idea there myself, but I think it comes down to the desire for power. Tom is master in the Old Forset, but he does not dominate...the Ring's power over a person is proportional to their desire to use it's power. If Tom has NO desire to use the Ring, it has no hold over him. That's what I think, anyway.
As for golberry, I don't know what her purpose is. I'm sure she has one. Mybe just to offset Tom's weirdness? I love him, but you have to admit, he's the Ned Flanders of Middle Earth.