No, no, wait! It can have a happy ending and still be dark. If the DEs got him, they aren't gonna kill him there. They'll haul him back to Voldemort for "questioning" and throw him in a deep dark dungeon, and Remus has to rescue him, and then... OK, I'll stop. :-D

The ambiguous end did kill me a little bit because it seemed so final, but that's the beauty of an ambiguous ending: if I want Snape to live, I can decide he did. But it does excite the curiosity.

Funny you did this. I've been thinking about posting some meta-thoughts on my own dark-fic since it brought up some uncomfortable but interesting questions. You may have inspired me.