There is no “before” in the big bang or any such model: multiverse, ekpyrotic cosmology, etc. The point of inception of ”all that there is” is outside of all physical laws including space and time.
The second disagreement is in the meaning of reality. In physics, “realism” refers to the idea that a particle has properties that exist even before they are measured. Here is a good description of the measurement problem.
There is much dispute over that which exists not only in metaphysics but also in physics. So reality is not definitive, or as Einstein said, Reality is an illusion, albeit a very persistent one.
With regard to your assertion that He necessarily must have created Himself - if you are truly interested in the subject, you might want to explore the concept of Ayn Sof which roughly means infinite and nothing. It is a Hebrew term used by Jewish Kabbalists to describe God at creation. The number zero is a parallel concept in math, infinite and yet nothing. Likewise a singularity is a parallel concept in physics, infinite and yet nothing.
You've implied that God exists in the physical realm.
The reason is that space/time is part of creation (it is created as the universe expands) – it therefore is not something in which the Creator exists.
You've implied that God does not exist in the physical realm.
My point in observing that God does not exist in reality leaves open the possibility for the existence of a God that transcends reality, a God much like that revered in Judaism.
Isn't it neat to live in a country where people are not burned at the stake for expressing thoughts like this?