I love the world of this story. It's so expanded from the world of canon, and there are hints that the edges of what we see in this story are merely the beginnings of extensions into more and more (as the real world is). And the characters are front and centre, as they should be, driving the plot and fulfilling the spaces as they need to be in a world that's healing from what was, at heart, a civil war.
David Yalçin, the Snitch, isn't quite a mystery (at least not to me), but that didn't detract from the pleasure of watching Viktor get to know him and discover his identity. And Viktor (oh Viktor) is still so full of determination, of a vision that narrows to his goal (whether that's a snitch or a war criminal) that he feels real.
They're so believable as evolutions of the characters we meet in canon, even to the end.
Unlike others, I'm not going to quote lines, because I'd be at this all day. This is just wonderful.
Oh, and one last thing, I love that you encapsulated the (true) ending in that single image of the ticket and left the rest to my imagination.