But if Gandalf,Saruman, and Sauron were all Maiar and affected by the power of the ring, shouldn't Bombadil be affected by it too? Am I straying into the Corner again?
It's possible that Bombadil is not affected by the Ring because he doesn't want anything. Gandalf wants Sauron gone, and ME free; Sauron and Saruman want power; others simply want the Ring itself. Bombadil wants nothing that he does not have, that's pretty clear. He's happy where he is.
But I admit, the idea that Bombadil is a Maia is almost as weak as some of the crazier ideas about Bombadil. (Bombadil is Iluvatar, Bombadil is Tolkien himself, Bombadil is a hallucination, Bombadil is the Witch-King of Angmar... every one of these theories has its proponents, you know.)