I actually have for you, several more points (which are my answers to certain questions in your post), including 'D', which is my answer for the Gondola Ride. Though first, I'll try to answer some of your questions confusion in these paragraphs.
To begin with, I'll go into what I think about the whole
Reality is what Wittgenstein would dictate to be "that which one can speak of", and to "remain silent" would refer to what's always been non-existent. So to Tomosane because she would represent Tomosane's true form 7 years ago, not some new form he tries to take that conflicts with another. Though I'll say that SubaHibi's portrayed world is his internal world, and I don't believe that Zakuro really exists in anyone elses' internal world but his.")
As for the new points (which are all once again interpretations I've made, so think of them however you like):
D). The Gondola Ride. Probably the single most to represent a mentally unstable person's subconscious feelings/thoughts towards being incomplete and discontinuous, laying in a hospital waiting either to get 'fixed' or to die. It being a spirit simulation ride would further make sense, as the person's current state of discontinuity could represent a spirit of their former self 'after dying'. Though SubaHibi's theme strives to show us that, whether broken or unbroken, every person lives equally as happily as each other. This particular scene tells us exactly what the term 'Endsky' refers to, as well. In any case, throughout RH1 and some other parts of the story, there were flashes of a hospital bed too... I wonder what that means for the full story given what the gondola ride is portraying?")
E). Regarding the Endsky concept and the story's mechanic. You may be aware of the . And with another, can there really be a true reachable limit of the world then?")
I'm not sure any of this really provides as an acceptable 'panacea' of clarity to all the mysteries that lie within SubaHibi. I tried to include my conclusion on the sole mechanic of the story is which I believe explains everything (as in, simplifies everything put together), but it went over the word/character limit of this post. I guess this will have to do for now.