Not everything happened inside the body, cedar forests grew inside? That's taking metaphor to an extreme.
I am not expecting you to agree with me, nor am I trying to persuade or convince anyone.
As I indicated, the size of the cedar forest is bigger than the Earth which indicates that it is not earthly. Naturally, such forests do not exist within the body. This forest is symbolic of a larger world which can only be entered from within.
The Epic describes the dangers inherent in the inward spiritual path. This warning was later adopted by the Egyptian priests and incorporated into the philosophy behind the God/King. Hence, the 42 Declarations of the Pharaoh prior to entering on his spiritual journey. And, later with the first two limbs of Ashtanga Yoga.
Gilgamesh was the son of a God (2/3) and a woman (1/3). He associated with Gods and those who had passed to the other side.
It's a mystical narrative.
I don't know what to say about your new age metaphysical viewpoint
Well, you could always try reading the Epic from this viewpoint and see if it resonates with you.