Thanks for sharing your experience, Vovin. I realize this thread it quite old now, but I thought I would still comment on it.
As I read through your account I actually got a little scared for you. You really pushed the envelope with everything there, one thing stacked on top of another, stacked on top of another (in terms of the fasting, float tank, computer monitor with imagery, binaural waterproof headphones, sweat lodge, etc. etc.) I wondered what you were looking for, or hoping to find, with such extremes.
Your experience in the black "sea of darkness" (the abyss) is one I vaguely remember myself before I was born, if you can believe that sort of thing (i.e.,vague, pre-birth psychedelic memories, coupled with scattered imagery of past lives). I revisited the lonely sea of darkness in an iboga ceremony where I was sure I'd died, and I found it striking how you called that place the same thing as I experienced: A sea of darkness, infinite and devoid of anything or anyone else but a 'awareness' with no concept of 'I'.
Through my ayahuasca and iboga experiences, I've come to believe that ultimately, behind all appearances of form and "beings," there is really only an infinite, intelligence awareness playing a sincere game of illusion with Itself. We are not separate from this force; we are It. In other words, there is only ever one of us in all times and places whatsoever, and through a process we do not understand nor need to understand, we are a being with an infinite number of points of awareness, only we can only experience them one at a time. I am you, you are me, and we are everywhere. Linear time is a particular perspective that allows us to experience the duality of separateness.
The sea of darkness, or however the experience of aloneness with the 'central self' comes on, is as natural a dimension to being God as sleeping and waking up are to being a human being. We naturally go through phases and we see phases around us everywhere in the cosmos: asleep; awake; alive; dead; duality; non duality. We might describe a shamanic death experience using different words or symbology, but your experience seems to closely mirror my own shamanic death experience with iboga, and places I've gotten to in the Bardo realm with ayahuasca.
You're a good writer. Happy New Year. Namaste!