5. In that sense, you came from nothing.
No, you come from whatever caused you. If I make a sphere out of clay, it doesn't matter that there's no "blueprint". I still made the sphere. It didn't "come out of nothing".
6. That is the sense that counts in our math, and
I have no idea what this is supposed to mean, but I am certain that whatever it means, it does
not lead to:
7. The denominator in the formula for my existence, given the scientific model, is ∞.
Because the denominator in the formula for your existence, given this scientific model,
is not and never will be ∞! The
universe is finite!
If we kept redoing the process, we'd keep getting different brains, and different selves.
If you kept doing the process, you'd keep getting
identical brains. Whether the "self" can be considered different or not is a matter of semantics, but, more importantly, is
irrelevant to your thesis.
If somehow, we could keep doing this forever, we would get new brains, and selves, forever.
This is where you went off the tracks. You can't keep doing it forever because
there's a finite number of possible arrangements of particles in the universe!
Everything else is irrelevant to this key point: There are only a finite number of potential arrangements of particles in the universe, therefore, there are only a finite number of selves that can exist, therefore, the probability of your existence does not and cannot have a denominator of infinity.
If the universe were infinite, then we'd be having a whole different argument. But it's not.