Sorry to intrude.
Br. Dawood your whole explanation is based on conjecture and your own wishful thinking.
Mere claim of revelation and the narration of revealed Ayats would have been sufficient for people to accuse and label Exalted Prophet, after all “revelation” in itself was an extraordinary phenomenon that would not have required Prophet’s explanation of his experience for doubting and ridiculing.
So your conclusion that 53:4 is referring to Prophets own words not revealed words is not based on very obvious context. QXP is very clear in this matter.
53:4 This (Qur'an) is but a Revelation that is being revealed to him.
Further, your statement that “Revelations not fully captured in the Quran were meant for prophet himself, teaching him, for example…….” Shows that like N2I you also believe in Angel Jibreel visited numerous times, according to some N2I scholar 23,000 times, sometime to reveal Quran and sometime with other purpose. Some of revelations were captured in Quran and some of it become Hadith-Qudsi. Wow!
Whole phenomenon of “Wahi” is beyond the comprehension of human mind; that is why “The Book” is one of the five constituents of Iman upon which we chose to believe. Anybody’s conclusion, claimed to be drawn from understanding of “process” of Revelation is nothing but misguidance.
Furthermore, your assertion “If anyone does not do these manasiks as Quran demands, he/she is not following the Quran, no matter what one says” is almost a “fatwa” of N2I scholar. By your reverence of “manasiks”, not found in Quran, you raised the level of those “manasiks” almost to the text of Quran of which Allah has taken guarantee.
Finally, my two cents:
Why Allah didn’t explained these so important “manasiks” in His Quran of which He has taken guarantee. Why He missed to provide the details of those so essential rituals in His “full detailed” Quran where He missed “nothing”?
In case of inheritance Allah explains in detail even to the extent of fractions, then why Allah didn’t said, “Pray five times a day” and “2 rakats in Fajr”, “4 in Dhur” etc.?
For so essential religious rituals, why Allah left humanity to deduce it from some Ayats instead of direct and clear command or depend upon “Tawatur – chain of continuity” whose reliability cannot be ascertained and guaranteed like words of “Quran”.