As you may have gathered, I am not in agreement with mainstream Egyptological thought. This includes all the myths attributed to Aten. I understand that it is extremely difficult to explain the origins of the Universe and a simplistic narration, such as the one which you have provided and which appears to be widely accepted, may suffice for some, but that myth is couched in symbolic language as an explanation of the unexplainable.
As for Osiris, Isis and Horus, it is my position that these names originally referred to certain stars about which I have posted my thoughts numerous times on this board. Somewhere during Egyptian history, these stars were anthropomorphized into Gods. The myth about Osiris being cut into fourteen pieces, Lebanon, the box etc. is surely symbolic - to take it literally is to suspend rational belief.
As for the size of the Djed Pillar, as you are aware, Egyptian iconography is rarely drawn to scale. The fact that ropes were necessary to raise the pillar could indicate that it may have equalled the height of an obelisk - a considerable height.
The meaning of the name of Djedefre has been corrupted by Egyptologists to suit their purpose of including him in the Khufu/Kafre/Giza milieu. So the praenomen of Djed, symbolized as a pillar, becomes "support", leading to "Re is his support." The whole context was then changed to "Enduring like Ra."
Quite simply, it could be translated as "A Pillar to Ra." This literal translation actually makes sense. Instead of building a pyramid to house his mortal remains, as claimed by the Old Antiquarians, Djedefre, in fact raised a pillar to Ra at Abu Roash. He raised a pillar to the Sun at Abu Roash. The Pillar to the Sun, or Djed Pillar, looks very much like a solar device designed to capture solar energy - Sun Power - The Power of Ra.
The connection with Giza could also include Heliopolis. The magnitude of Zawyet el Aryan requires much deliberation as it is probably the most significant site in Egypt. I shall leave it there for the moment.