Wow. That was beautiful. Your Sam is heartbreaking. It's how I see Sam. I wrote also about the "burning" of having an angel within. Interesting that it's perceived that way.

I found so many incredible passages that just were stellar. I picked out a couple of favorites.

This: He takes a page from Dean's book, finds a way to piece himself back together, all duct tape and chewing gum and dirty string and sheer Winchester stubbornness, and God help him he wills himself to hold together, because Dean is crying and needs him and he's being consumed right under Sam's eyes, and Sam won't let him go. Not without a fight.
--- lovely language. perfect

this: He puts a hand on Bobby's shoulder in a mute apology, feels Bobby's callused fingers over his, accepting the apology without a moment's hesitation (just like Dean, his mind whispers), and the tightness in his chest eases, just a little bit.
--- the just like Dean part. Yes!

this: He starts teasing Sam gently about hovering, a few good-natured jabs that are so very much like the Dean from before that it's all Sam can do not to scratch out his own eyes or cry until there's nothing left, because he wants this, he wants it so badly it's like blood filling his mouth and spilling from his eyes like tears, and he just isn't sure that Dean isn't putting it all on for him. Because the Dean from before would do anything, anything to give Sammy what he wants.
-- made me cry

And you ending? Superb.