Loyalty Quotes in The Hobbit, or, There and Back Again

How we cite our quotes: Citations follow this format: (Chapter.Paragraph)

Quote #1

[Bilbo] still wandered on, out of the little high valley, over its bulge, and down the slopes beyond; but all the while a very uncomfortable thought was growing inside him. He wondered whether he ought not, now he had a magic ring, to go back into the horrible, horrible tunnels and look for his friends. He had just made up his mind that it was his duty, and that he must turn back – and very miserable he felt about it – when he heard voices. (6.3)

After Bilbo emerges from the Misty Mountains, he has "a very uncomfortable thought" that he should go back and check on Thorin & Co. to make sure they get away from the goblins OK. Is this the first time we see Bilbo feel a real sense of duty to the dwarves? When do they start to act like a real group with Bilbo included?

Quote #2

Gandalf answered angrily: "I brought him, and I don't bring things that are of no use. Either you help me to look for him, or I go and leave you here to get out of the mess as best you can yourselves. If we can only find him again, you will thank me before all is over." (6.9)

Here, Gandalf's insisting that the dwarves go back into the goblin tunnels to help him find Bilbo. Gandalf is incredibly loyal to Bilbo from the start; in fact, his loyalty to Bilbo is what makes Bilbo decide to join the dwarves in the first place. Do we get any indication about what Gandalf sees in Bilbo that convinces him that the dwarves "will thank [him] before all is over"? What is Gandalf's history with the hobbits and with Bilbo's family in particular?

Quote #3

It is no use arguing. I have, as I told you, some pressing business away south; and I am already late through bothering with you people. We may meet again before all is over, and then again of course we may not. That depends on your luck and on your courage and sense; and I am sending Mr. Baggins with you. I have told you before that he has more about him than you guess, and you will find that out before long. So cheer up Bilbo and don't look so glum. Cheer up Thorin and Company! This is your expedition after all. (7.36)

Gandalf appears to be a guide for Thorin & Co. strictly for his own interest; he certainly hasn't been hired by Thorin, as Bilbo has. So Gandalf can come and go as he pleases. What sense do you get of Gandalf's relationship to Thorin & Co.? What reasons might he have had for joining this quest in the first place? Why might Tolkien be leaving it up to us to imagine how this whole quest got started with Thorin and Gandalf?