Oh the pain.
Cause they're both right - Dean did it to save Sam's life, ignoring he was being played by the angel and Sam feels betrayed by Dean- and both wrong, cause Dean needs to say he's sorry and Sam needs to forgive. They just don't know how to be apart from each other and horrible things happen when they're not side by side.
Sam caressing Baby broke my heart; he might not say it out loud, but he loves that car (their true home) just as much as Dean.
Lovely, lovely start, love the way you write the boys.