As you say, ‘duality begets duality begets duality’; It’s ‘turtles all the way down’. The prime polarity where ONE split into TWO and yet remained, can only be theoretical to us. We are too far down the pile and too fragmented to ever approach this.
We can get the ‘flavour’ though, because this is a fractal process so we can taste and work with dualities on many levels. It is bitter work however because on the one hand the polarities long to be united and on the other hand they fiercely resist being brought together.
I suspect we are ‘larger’ entities than we imagine, spanning several ‘worlds’. If we are focussed on a particular world, it becomes real and others appear illusory. To the lucid dreamer, the waking world appears illusive.
I think you are right about the prime polarity that we are tasked to ‘work’ with: Consciousness and the unconscious. This is dark and dangerous work. ‘Here be dragons!’ This is something akin to soul retrieval. Gathering together the dismembered parts and becoming ‘whole’ (again).
Neptunian influence sounds good. You are well down the rabbit hole!
With Sun and Mercury in Capricorn, I am perched on the edge, looking down with a pair of binoculars! Moon in Pisces, Mars in Aquarius and Scorpio ascendant might give me a bit of added interest in this sort of stuff though.