Of course, reading the comments pointed out some things that I hadn't quite noticed in that context... I can see how it could be a dark fic, especially if taken further. And it does already have hints of that anyway - I'm very used to possessiveness in fics on one or both their parts (even when it's a sub!Harry, since submission does not mean not being jealous or possessive. Interesting idea there...), so Harry's reaction to Bill and all didn't seem so chilling. But if you look at it from a different angle-- Yeah, just a bit off kilter there. *g*
And then even if they worked it out nicely between the two of them, there's all the outside influence, and the fact that modern society is very up in arms about this sort of thing (a fact that canon fics can get around in multitudous ways, haha) makes it like a ticking time bomb. No matter how careful, something's gonna leak, and then... Woosh! *thoughtful* Thinking from it at that angle, it could either end up resolved, with both of them weathering it and maybe better for it, or the whole damn thing ending messily. Possibly literally, with blood and guts, and an excess of teenage drama and angst.
With that in mind, I have to think that you found just the perfect place to stop it: them having slid down a bit of a hill and teetering on the edge of a precipice, but fairly content and not falling, not just yet. :P It would be interesting to see if such a thing could be resolved into even a bittersweet ending...
I still love it and it still makes me squeeful, though! (<-- Is a bit messed up, probably. *g*)