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 'delusion' matter. I'd say the difference between Takuji!Tomosane and what makes him delusional in nature, with Zakuro who is not, has to do with the plot-related fact that Takuji as Tomosane's personality was built to epitomize and represent Tomosane's pure self-denial. 7 years ago, during that very incident, Tomosane believed that just maybe the power of the Messiah was required to undo for him, the tragedies that took place. Tomosane's self-denial is then evident in that he tries to create a new 'reality' (a new set of values) that conflicts with his previously known one, thus forming what a 'delusion' is. That in turn, also causes Tomosane to become discontinuous in nature.
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 one really only has their own internal world and what they "so choose to/want to see" exists as such, unless it's conflicted. Like Tomosane 7 years ago, everything the Takuji personality stood for was denied by that very personality underneath as well. The thoughts/feelings he has before he becomes the Messiah in Invention root themselves to conflict with the thoughts he has after he becomes the Messiah. Ayana did in fact say that he was trying to steal the role of the Destroyer when he was originally positioned as the Creator. If point 'C' in my previous post is anything to go by, then Zakuro does not appear as a delusion (or delusional) 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):
Here's a point you raised in your previous post that I hadn't got to answer. About the Gondola Ride. Probably the single most relevant scene to what SubaHibi's plot 'is' beneath the surface. The basis for my every one of my wacky ideas came from interpreting this scene, actually. The scene details an amusement park ride which simulates the 'feeling of being a ghost', showing normal lifestyles having "ended", a hospital being the final resting place, and the fact that there would be no true end to it all afterwards. The entire scene seems (to me) 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?
Regarding the Endsky concept and the story's mechanic. You may be aware of the 1999 VN that Sca-ji created as a sort of experiment, 終ノ空? It was certainly a cult classic, but to the mainstream audience and later on to Sca-ji himself, it was considered incomplete. I guess I'll say that, SubaHibi isn't just a remake of TnS, but in a way, also a sequel. I wouldn't recommend actually picking it up and playing it, though. It's merely the previous version of RH2, Invention, and Insects, and then it ends. By the way, that's where SubaHibi's surface structural issues rise (besides what you can interpret of the story). SubaHibi is essentially two VNs into one, with the latter three chapters and RH1 being the actual SubaHibi lol.Aside from that though, the original 終ノ空's main concept (and perhaps statement) was this 'Endsky' term. In detail, the term can be thought as "the sky of a scripted/doomed to end world", which is representative of, once again, the perception of the world from a state of discontinuity. And basically, the delusional/religious-minded people who've become 'broken' share this state of mind. In believing the world will end due to their discontinuity, they also believe the sky above their heads is the one and only Endsky, and that they can reach the end. SubaHibi's concept and statement is opposite to this, and overturns it by showing us what's beyond the supposedly reachable 'limit of the world', another Endsky (終ノ空II). 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.