God is omnipotent means that God can do everything that is logically possible. But the question is: is there any sort of reason to think that things can come into existence from nothing? I have never heard of one.
What you need is a logically possible way for one entity to transform nothingness into something.
Which is fine, because theists do not believe that nothing existed before the creation of the universe. They believe that God existed.
I said “out of which”. If the universe is made out of God, then God changes.
Instability of nothingness is such a condition. Lots of philosophers belive that nothingness is necessarily unstable, and that sort of condition could in principle result in nothingness becoming something.
The instability you attribute to “nothingness” is misleading. True Nothing has no properties, and instability is a property, so true Nothing can’t have it. The instability you refer to is a property of empty space, or vacuum, or zero-point-energy field. Space is not, in fact, “nothing.” It is space, which physicists believe to be a “quantum foam.” Zero-point energy is in fact a form of energy, and from this energy, particles (e.g. positron-electron pairs) can be observed “popping into existence.” But this is not “something from nothing,” rather, it is matter from energy.
There are countless heresies based on Emanationism, to which you refer above without naming it as such. Simon Magus has been called the “father of all heretics,” and his scheme is called Simonianism, you can look it up and see for yourself how much it has in common with other variants of Emanationsim like Kabbalah and Advaita Vedanta.
Essentially, all such schemas boil down to a human attempt to explain the Mystery of Creation. Human beings cannot produce something from nothing, but God can. It is human incredulty that God can, that causes humans to attempt to explain Creation in two different but similar ways: either, as modification of some pre-existing proto-matter, or, as God’s modification of His Own Substance. Which, when it comes down to it, might be the same thing after all, so maybe these are not two different ways but only one way expressed two ways verbally.
It is understandable that you and others would want to do this. Our intellects are designed to seek explanations that we can grasp. Our intuition is that something cannot come from nothing, and our experience is that in creating anything, ourselves, we need pre-existing material. If it is posited that at one time, or more accurately in eternity before time, God alone existed, then it is logical to conclude, given the above, that He must have created everything from His own Substance.
This is, of course, Pantheism. That which begins as God’s Substance cannot cease to be God’s Substance by undergoing modification. That is the basis of our belief that Mary is the Mother of God, and that Jesus is God. Since the Word is consubstantial with the Father, He cannot cease to be consubstantial with the Father by undergoing the modification of becoming a human being. He is fully human but He does not cease to be, at the same time, fully God. The Catholic Faith does assert this of Jesus. But if she asserts this of Jesus, and at the same time asserts it of every particle of matter in the universe, then what becomes of the doctrine of Jesus as the unique Son of God? Plainly, it becomes meaningless. If “everything is God,” then there can be no way in which Jesus is “especially God.”
Consequently, Christianity is incompatible with the doctrine of Pantheism, and since Pantheism is the logical outcome of Emanationism, Christianity is likewise incompatible with Emanationism. It is inconsistent with the unique status of Jesus Christ as the only-begotten Son of God, to assert that God made the universe out of His Own Substance. Consubstantiality with the Father is reserved only to the Son and the Holy Spirit, and God says,
Isaias 42:8 I am the Lord: that is my name: and my glory will I not give to another. . .
Since there was nothing at all in existence apart from God before (i.e., in eternity before) God began to create, consequently, God made everything from nothing. This is not to be misconstrued as Space or Vacuum or “Nothingness,” as if “nothing” were some particular kind of substance. Nothing means literally not any thing. Space or Vacuum is in fact a created entity, a substance in its own right, as Quantum Physics confirms. Eternity before Creation includes “before” the creation of time and space, as created entities. God created these also, from nothing.