[Imladris]

I don't quite understand what you mean when you ask, "What did Frodo grow into?" He didn't grow into anything at all. When you grow like Frodo did, you gain understanding of the world and how it operates. You don't grow into a different, super spiritual person.

Yes, Frodo did give it up. I believe that this has been said before, but Frodo made a conscious descision to continue his quest. Thus, he willingly gave up everything he lost (his innocense, etc). But you're forgetting that he gained so much more than he lost. He gained the joy of seeing the hobbits in peace, of seeing Middle-earth saved. He gained understanding of pity and mercy.

I do not believe that Frodo cast the Shire away like orc gear, that he viewed the hobbit ways as uncouth. That is against his very nature, and the ending would have been infused with hate, which it wasn't.

Frodo suffered much, gained much, saved much. As a reward, he went to Valinor. That's all what happened. It was the only place he could go that would ease his suffering. Isn't that worth the pain, living your life out with Bilbo and the elves? Of course, it doesn't say that his troubles were relieved, but I believe that is heavily understated.