Angels don't notice that? There's a distinct scent that human souls give off. I don't know how to describe it, there's nothing in any language to describe it, but it's there. Dean in particular is a bit corroded. It wasn't always, but at some point, it's scent changed. I don't know how else to explain it.
I'll be that person. Cas has gone through too much to have Deano stepping all over him and treating him like crap. It's not happening here. We stayed away from the Winchesters for a goddamned reason.
I wouldn't. But if it becomes an issue, that's different. I think Cas might be upset if something happened to him, so. . .there's that. And I honestly don't care if he's alive so long as he leaves me alone. Which seems to be a thing he has trouble doing. There's the added bonus of different realities, so there's no telling what any of us did in his reality versus our own.