Your first paragraph raises important questions.

Every aspect of Creation is indeed a single cell but, if the Holographic Universe theory is correct, each cell contains the whole in some sense; it's just a very limited, scaled down, imperfect version of the whole picture. If the totality of God were incarnated into one human being at one point in history, that would raise difficult and impossible-to-answer questions:

How can that be achieved while bypassing the hologram effect?

How is that different from any other human being who is also a hologram of Divinity?

How is the universe being sustained in being while the source is incarnated into the physical level?

I think that Christianity doesn't think about such questions deeply enough. It starts from the problem of not believing in the ultimately divine nature of humans (as in the Perennial Philosophy), therefore believing that we need the divine intervention of Jesus to save us.

Now for your second paragraph. If 'gods' are ETs, that's going down the line of the Ancient Aliens argument; in ancient times, if beings descended in spaceships, with advanced technological powers which appear as magic, then primitive humans would think of them as gods/goddesses. That may be part of the picture, but is not the only explanation for deities.

You talk of beings “from other dimensions”. I assume you think that ETs exist on the physical plane. Humans seem to be able to see them, but they may perhaps be interdimensional, something along the lines of ghosts and apparitions?

Some people believe in all sorts of beings from other dimensions: elementals, demons, jinn as in Islam, angels etc. Gods/goddesses are simply one more item on the list, but they would presumably inhabit a very high dimension, much closer to the source. If that's true, then there would be no need to connect them with ETs,