Is cellular memory created or held within the DNA, and if so, is it not part of the conventional helical structure science knows about, but rather in the extra dimensional DNA of the person?

This you have seen intuitively to be the case and it does explain how there can be special properties, special capabilities, and have an extraordinary nature simply arising from prosaic chemical constituents which, after all, are the prosaic makeup of the molecules of DNA. There is indeed more happening here and that is the explanation. There is an energy field comprising a vaster amount of information that is part of the official genetic makeup and tracks with the genome and its expression within an individual human being, and is modulated accordingly so that it is a perfect complement to the individual, in all respects, and has much individual makeup tailored to their history, their personality, their karmic destiny, and the soul characteristics needing to project through the DNA itself to make things happen in the physical body for the living person. DNA is the gateway for soul expression, but it is via these two levels—one profound in its information content within the double helix itself, and the other a much vaster energetic field of knowledge and information linked to the physical DNA, but also to the soul and the akashic records, both. That constitutes a much larger library about the person’s individual makeup and governs much of what happens during the person’s life, both with respect to their physical body and its variable functioning as well as the thoughts, beliefs, and choices enacted through the day‑to‑day life of the person.