I would argue that mathematics and logic are independent of issues of the existence or non-existence of God. Consider the following question. Can God create a universe/reality where 2 + 2 = 3 or 5. I maintain that the answer is a resounding no! The axioms of arithmetic (which are restated as the foundation of all mathematics - check the first chapter of any advanced textbook or treatise from algebra on) are abstractions (not in the 'abstract art' sense) of the rules by which physical objects combine. To create a reality in which 2 + 2 = 3 or 5 would require magic/supernatural powers to change what was already four somehow to three or five, and to adjust the perceptions of all observers. I invite any theist to credibly argue for such a reality.
The known and unknown laws of physics are described by logical and mathematical constructs that model physical existence and so are independent of the holy, spiritual, or supernatural. God in/from/of an unknowable reality in acting on/through natural things is constrained by natural law in order to interact with it. Theists then have a diminished basis for claiming that God is not subject to physical limitations or is in a realm beyond human comprehension. I invite any theist to credibly argue against such limitations.
*By which I mean any definition that satisfies the reader.
I grok your point (a). As for (b), at least per the cataclysmic consequences, certainly science fiction writers through and beyond Star Trek to scientists such as Brian Greene have imagined phenomena such as universe/hyperspace/subspace bubbles insulated from other realities. Now, in each fictional instance a mechanism, often plausible, is offered the reader. You offer a declarative statement as though it were a fact. Scientifically, how would you justify that statement?
And, if God is part of the universe, creation of the universe becomes quite a conundrum.
Aside from technical meanings of 'potential', the term connotes 'possibility'. Perhaps the closest thing to that idea that we can name is quantum randomness. Now, exactly how that would work I cannot say for certain (a Nobel if I could!), but self-creation via quantum randomness appeals to my inner Occam far more than a self-created, all powerful, intelligent creator of everything else.
I also like the concept of potential as an inherent state in the universe. To me it's obvious – were there no conditions of potentiality from which extant reality emerged, there would be no current reality. The potential(s) must conform to physical constants of the universe (whether we are aware of them or not) - If they don't then they are irrelevant. An all powerful entity running the side show doesn't fit that criteria. How silly is the idea that such a being would create a universe in which he couldn't exist?
The unit of probability you posit would have to be a statistical expression - I don't think an absolute measure could be established.
Because science is about finding mathematical models that have predictive power. Perhaps the closest anyone has come to a predictive TOE is Stephen Hawking and associates in discovering a string theory model using negative space-time curvature, very much like in M. C. Escher's work, that produces, via a quantum probability function, an expanding universe and may have predictable results unlike current string theory that uses a positive curvature. Unfortunately we cannot just come up with a clever term such as 'potential' and pronounce it a TOE.