As is typical, quoting without understanding.
Ambiguous quotes from Justin Martyr taken without full context. He hardly states the Mormon position on creation, does not say that God did not create matter. On the contrary, he has contemporaries, even students, who are more explicit about ex nihilo creation
(Tatian and Theophilus). Justin WAS a Platonist, so maybe he did hold Plato’s pre-existent matter theory – but boy, what a nasty shock to your stated position that Mormonism is “pre-Hellenized” Christianity, for this (and much of the rest of Gnosticism and poly- or heno-theism) is Hellenic…
Of course, the Scriptures themselves really offer a lot here, followed up consistently through Judeo-Christian thought. John 1, many places in Paul’s letters, some references to God’s creation in Psalms, etc. And very explicit in 2 Maccabees 7:28: “I beg you, my child, to look at the heaven and the earth and see everything that is in them, and recognize that God did not make them out of things that existed.
h And in the same way the human race came into being.”
You might find these interesting:
Blogging Scripture HIS Way: Creatio ex nihilo: A Critique of the Mormon Doctrine of Creation
https://carm.org/did-god-create-the-universe-from-nothing
Catholic doctrine includes “deification” or “apotheosis,” but we mean something very different from the Mormon interpretation. For it is as Paul says, we are made “partakers” of the divine nature. It is union with God, elevation in that union through Christ. It is not that we become superpower gods over our own worlds, equal to God. That is an alien concept to Judaism and Christianity, and would have been received as the highest blasphemy and abomination.
Similarly, with the relationship of the Son to the Father; precise Trinitarian formulations, stated in ways that do make for improper analogies, were centuries off in Justin’s time. He did not state that Jesus was a separate god. As the Arian Heresy revealed, that was an innovation. The People of God had always believed in the One-ness of God, as well as the Three Persons, without yet having worked out precise details. But they knew what the Apostles taught, and they were stubbornly insistent on that, and that lead to understanding of what God was NOT.
This is gone into in some depth in the book I mentioned. The imaginative descriptions are the Author’s attempts to put the reader in the time and place, and make the historical people involved more approachable and real, not just names in a dusty ancient source. He doesn’t spend much time on that kind of narrative, really. He spends much more time, particularly after he has set the stage early in the book, with the actual back and forth, including many quotations from the original sources, on both sides.