You wrote: “I repeat, the above does not say he had other none Quranic revelation, or that these relate to his telling others he had received revelation. It is obvious he told everyone he had received revelation, but what he was repeating to them was the revelation, the Quran, and other than the Quran he had no revelation.”
It is obvious my brother, either I failed to clarify my understanding or you failed to grasp it. Let me take a trivial example first and then will go into some linguistic details. Suppose you received verses X, Y, Z. This was an extraordinary event for you as well as your family and friends. You tell your family and friends that these verses “X, Y, Z” are revealed to me. Would they simply take it or ask you some questions? Obviously they will ask you questions like this: we believe in you, tell us a bit more about your experience, what happened, who came to you, how these were revealed etc. etc. Thus, you respond with what happened, explaining them all you experienced, felt, saw, heard, etc.
Your explanation of what happened is human speech, Nataq, in Arabic. This is the word used in 53:3. Thus, when prophet explained and provided details about his first-ever encounter with angel Gabriel, people started labeling him: he lost his mind, he erred, he is confused, perplexed, his desires are not fulfilled, he is frustrated, etc. 53:2-3 are comprehensively addressing all such labels. 53:4 is simply referring back to this speech/explanation/details of prophet including verses revealed if any, and stating, it is indeed Wahi, revelation. The word “huwa” in 53:4 is clearly referring back to the speech of the exalted prophet. Quran or Book are nowhere found in these verses. Thus, undoubtedly, 53:4 is not referring to the verses of Quran only. This is further strengthened when God clearly states in 53:10 – he revealed to His servant what he revealed. Thus, in this first-ever extraordinary encounter, angel Gabriel not only revealed some verses of the Quran, he also revealed what is Eman, who is God, who is angel Gabriel etc. etc. All such things are covered in 53:10.
You wrote: “There is no verse in the Quran stating that Allah revealed the Quran and something else, so we cannot accept anything other than the Quran.”
I am not asking you to accept anything besides Quran. Revelations not fully captured in the Quran were meant for prophet himself, teaching him, for example, how to read/write, how to pray, what are correct manasiks to be followed, etc., else he (prophet) could not have fully followed the Quran. Muslims at the time were asked to follow him. Thus, when he did wudu, stood to pray, then prayed, he was following the Wahi including Quran, for it is Quran asking him to follow the creed of Ibrahim. When Muslims stood behind him and prayed, they were following three things in one go, namely, creed of Ibrahim, the exalted prophet, and the Quran. Thus, Ibrahimic manasiks were followed by the prophet as demanded by Quran, so did companions behind him, and continuing till date. If anyone does not do these manasiks as Quran demands, he/she is not following the Quran, no matter what one says.
Similarly, Taurah or Injeel too contain manasiks related to the religion of those who follow them, see 22:67. You are perhaps confused by the word “Hukm” in 5:44 etc., which is an order to do judgement between people based on Quran. Manasiks are religious practices, whereas judgements are to settle disputes between people, to safeguard their rights. The latter is an aspect of law, constitution. Thus, prophet was asked to judge between the people through the Quranic law, which he did. In matter of disputes, Muslims have to do the same.