Genuinely, after going through this, I feel like we need more trans based horror. Coming from a transmasc guy who loves horror, this feels like so much potential. Maybe it's just me, but I feel like the true ending is a dream or fantasy for an easier way to transition. Cliche yes, but as someone who's had occasional shapeshifter dreams that I vaguely remember, I could definitely see it.
(Sidenote do not trust the shapeshifter dreams. They will likely give you gender pain.)