There is some of my theories:
Auri must have something to do witth the fae, there is to much connection between the moon and her, beside her description looks like the one the mercenary woman gives when she talk about the moon, and I don't think Elodin would have try to befriend her for so long if she wasn't important. It is not a thing that is kept behind the Door of stone, I think it is a person, maybe it is Iax, the man who stole the moon, I believe that Felurian mention that it was for that reason that the Creation war started and that he is now locked away. So Kvothe may have open the doors later in is story, Iax got out (That's why Chronicler said on TNOW: "Some said there is a new chandrain with hair as raid as the blood he spills") and that would explain why there are creatures who have desapere thousands of year ago (probably at the end of the war) who appera now like the skin dancers.
At the question what stoped the chandrian from killing kvothe, my theory is linked to the fact everybody think that his mother was a Lockless, Thelu's angel probably came to stop the chandrians, if his mother was a lockless, since there family was entrusted with some important heirloom that's connected to the Chandrian, it's probable that some of thelu's angel protected her in a way and they got there to late to save her. Remember the description of the angels in TNOW "with wings of fire and shadows", and remember the story of kvothe in tarbean during the midwinter pegeantry when he almost dye of cold, he talked about a bird of fire and shadow who put its wings around him, making him warm. I think one or more of Thelu's angals is following him for his own protection, and that's why Skarpi new who he was and where he lived at Tarbean, Skarpi knows Thelu, he said himself "Thelu always say..." just before bieng stop by the Justice. The young girl from Trebon told kvothe "An angel gave me these dreams" and the chief of the bandits during the fight stopped and was like listening to something, exactly what the Chandrian did when they kill is parents just before Halyax "said they are coming". So it wasn't kvothe who brought down the thunder, but one of thelu's angels.
Now I want you to consider this, Elodin seemed scared when he thought Kvothe or Fela had changed their names, he thought that was dangerous, so it is dangerous for a namer to change his name. Then what about Chronicler, he is a namer and he said "I left the name Devan behind me long ago and I haven't though of myself as Devan for ages". He is a namer and his real name is Deva Lochees, that sound a lot like Lochless, the Maer's Doctor told kvothe that some of the braches from the Lochless family change their names a bit like Lochloe or something like that, Chronicler could be more that what meet the eyes, and it's maybe not a coincidence if the guy who stole his gear and his horse ended up as a zombie a day later. It would not be surprising that the "Great Debonker" as kvothe called him, had try to prove that the chandrian doesn't exist and he maybe meet them and where changed, he said to kvothe in TWMF "You wouldn't have liked me when I was at the university, I was a petulant brat, but I learnt more on the road that at the university". I fear all of them have something to hide.
About kvothe being young, I think he is and he he isn't, remember, he said I am older, he spent some time in the fae with felurian, and he certainly didn't meet Bast in the human world so I guess he could be young by it's time spent in the human world (maybe 18 years old) and older by his time spent in the fae.
About the door, remember what Haliax told Selitos, "No door can stay closed in front of me" that's why he can't sleep, forget, get mad or die, his name prevent him from all of the 4 doors and he what he is looking for is the door of stone in order to open them, trouble is Selitos and the oder namers must have made those doors in a way that he need some one special to open them, hence the to poem about the Lady Lackless, only Kvothe "the son who brings the blood can open it" and the flood will come, maybe a new war. You must remember what the book of the path sayd, Thelu, sent all the demons in the nameless void, with them Encanis (Iax) their chief. The chadrians are supposed to be those who refused Thelu's proposal, they wern't demons, so they just want to release the demon who were locked away, end the nameless void must be the doors of stone.
