Vico:
splegrand:
You wrote: “So I still come back to the only form, if you will, was the triune God. …”
Per Saint Thomas Aquinas, God is not composed of matter and form.
You wrote: “is it correct logically to say that all existence flows from the eternal pre-existence of God? With the understanding that no part of God was taken to create any other existence.”
Note also the Vatican I dogma of faith
On God, The Creator Of All Things."
Canon 4. If anyone shall say that finite things, both corporeal and spiritual, or at least spiritual, have emanated from the Divine substance; or that the Divine essence, by the manifestation and evolution of itself, becomes all things; or, lastly, that God is a universal or indefinite being, which by determining itself constitutes the universality of things, distinct according to genera, species and individuals; let him be anathema.
The Vatican 1 quote seems to be addressing Spinozan Monism, the belief that all being is made of God’s substance and just exists under different aspects.
The idea that all non-Divine being flows from God (from his creative action and not the molding of the Divine Substance) is orthodox.
More generally speaking, back to the original question, when we say God created ex nihilo we mean that God created all of the things he created without using pre-existing material. We don’t mean that the things he created came from nothing. They came from his creative action, from God as their cause.