I'm not a writer, so take what I say with a grain of salt. Also (as you may notice) my English is rusty, so that may affect my experience.
The main character's dialogue during the first part felt artificial. Maybe it's the choice of words, or the character's attitude. I believe it's because the character responds to their own thoughts with lines like "I don't care", "Enough of that", "None of it matters now."
If the character doesn't care, why should I? Why mention it even? I know it's denial, but there should be some other way of expressing that, so I don't lose interest in whatever the text is saying.
Hope that answers the questions. It's quite hard to express things when it's not in your area of expertise.
I like the world you built, the places seem almost out of a horror film/game and the plot/story is good. What's happening is in the back of your mind, but you don't quite expect it. And I like that you're not particularly explicit about what happened to this person after the event. Like the body modifications impacting memory. I probably missed some things during my playthrough though.
Although I mentioned it, I'm not sure whether another ending would work, cause you kind of wrap everything up nicely there.