Eryk of the Stonewards

I think he started his bonding during his time in Amaram's army. This would be the first time where he really showed himself to be honorable, putting himself on the line for inexperienced youths, sparing injured enemies and the like. This is also supported by Syl's memories, she says she remembers his time in the army but vaugely. I think this means it was early on in her development rather than years after following him around. His comments about the skies being his could just be a bluff or boast. It could also be a belief or subconscious ideas that the sky is his birthright as a Windrunner. Also possibly his ability of storm riding may give him the impression that he has a great ability to move about in the air.

Since Lightsong is one of my favorite characters in the Cosmere I will always try to find reasons behind his actions. I agree that due to his upbringing as a Returned he has been sheltered. But I think he really just wants to do something on his own. At this point he has been feeling useless and has made up his own backstory to justify his title. He believes that his latent abilities will show themselves once he is in danger. Because of all this I think Lightsong overestimates his abilities (obviously) and makes a blunder that many overeager young heroes make. I mean it really could have happened to anybody!

I think after all the torture combined with the others leaving made his resolve break. He is a hypocrite and I think he knows it, his drive for justice now is his attempt at redemption. He knows it's not enough, he lies to himself believing he is stopping the Desolation. I believe we will find all of the Heralds broken in some way.

Possibly Dalinar is flabbergasted by the planet spinning and not by it's roundness. They may still have the idea that Suns orbit planets.