So. I finally managed to get all endings for this. A couple of comments:
* The writing is really excellent, probably the best I've seen here so far. Oh well, I noticed two typos. Not a problem.
* The scenario is great too, I especially love the early branching that can give you very different facets, and the epilogue.
* The music is also a winner, it fits perfectly and is in itself very good. I really credit the music for setting this game's mood first and foremost, and I wish there were more people trying music more off the beaten path. The sound effects are... okay, I guess.
Now, for the not so good.
* The art... well. The style doesn't fit. And the mismatch does not work for me as an effect at all, and the mood is there in spite of the art, not because of it (mostly, as said above, due to the music). Not much more to say apart from that I think that yes, it's good on its own, yes, you get used to it, but it would still have been better with another style. Apart from that, there are a couple of things that are not a matter of taste, even disregarding that the backgrounds will change (because they obviously clash in terms of look and perspective); for example, some sprites are drawn in completely different perspectives. Compare Danny and Julius.
* The game is ridiculously hard. No, seriously. I think the whole binary tree has exactly ONE path that gets you the true end, and the choices are not obvious at all. I really do believe you're trying to be too clever here, what is apparent to you may not be so to most other people. Yes, it makes some sense, but only in hindsight, really. I only managed to beat it by setting the game into developer mode and tracing the variables, and even THAT does not help much without the hints you dropped in this thread and finally decompiling part of the game logic. I think it does say a lot about your writing that I even bothered with that, but it also says a lot about how hard it is. Not to mention that not getting the true end is totally not trivial, reading it is fundamental to getting the most out of the game, as you surely are aware. You're pretty much locking out a large part of the audience (as evidenced in this thread) for the sake of making some kind of statement.... not a good idea IMO. This leads us nicely to....
* Spoiler territory.
The twist. I saw this one coming from so far away it isn't even funny. I groaned at the thought of a NO GABRIELLE YOU ARE THE HALLUCINATIONS ending about five minutes in, and bam, there it is. To the game's credit, it really leads up its twist well, and in itself the ending is as well-executed as the rest of the writing, but no work exists in a vacuum, and this type of twist is so common that you always expect it. In fact, I think the game would have fared much better with a deliberate anti-twist. This is not at all helped by the fact that the ending is so aggravating to get.
Back to the branching, timed choices you have to wait out without any indication that this is the case is really just nasty. So is having choices with no feedback that are extremely important. And DOUBLY so is blocking rollback on those and only those choices.
* Using mixed-mode NVL and ADV is fine, but you really should consider clearing the NVL buffer after showing ADV text. It's pretty confusing to see old text again, with no hint that ADV text came in between. Now this could easily be another stylistic choice, but if so, it's not a good one. Also, the NVL text ran off the bottom off the screen in a couple of instances. There's a chance that it's due to the way I ran the game (on OS X with Ren'Py 6.9.3), if so, disregard that.
* Seeing how close to completion this is, I really wonder why you would release it nearly, but not quite, finished. It's not like you seem to be open to general suggestions regarding the concept at this point.
* Minor miscellany: The UI is stock. This in itself is okay, but you should at least consider using a different background for main menu screens. Also, I don't really like how easy it is to skip the credits by mistake, in a game where you're going to skip a whole lot due to the number of tries a certain ending will take to get. And there is no "the" Creative Commons License, there are several to choose from; to make sense, you have to specify which one.
But all in all, really quite an excellent piece that could have been among the best OELVNs ever (and to be honest, probably still is). However, somehow this only makes the above flaws all the more disappointing (especially considering some are by design). It's great, but could easily have been much better still.