Jesus and Greek Philosophy
Your question is worthy; It makes me nervous to venture a reply, but I will try.
I take your point that invoking a single creator is to locate the source of evil within the creation. One big difference between the story of Genesis and Timaeus is that the Creator and Man have a direct interaction with each other that changes over time in the first story while the Craftsman of the Timaeus brings all the components of the world into the realm of Becoming and that structure does not change even though our experience within it does.
There is a myth of the age of man's innocence in Plato's Statesman. It consits of the Pilot reversing the motion of the entire cosmos when disorder threatened its existence. Time and growth go backwards in the repair sessions. Once the place is reset, time runs forward again, and the Pilot lets go of the tiller. Our age is described as such:
For men, deprived of the care of the deity who had possessed and tended us, since most of the beasts who were by nature unfriendly had grown fierce, and they themselves were feeble and unprotected, were ravaged by the beasts [274c] and were in the first ages still without resources or skill; the food which had formerly offered itself freely had failed them, and they did not yet know how to provide for themselves, because no necessity had hitherto compelled them. On all these accounts they were in great straits; and that is the reason why the gifts of the gods that are told of in the old traditions were given us with the needful information and instruction,—fire by Prometheus, the arts by Hephaestus and the goddess who is his fellow-artisan, seeds and plants by other deities.1 [274d] And from these has arisen all that constitutes human life, since, as I said a moment ago, the care of the gods had failed men and they had to direct their own lives and take care of themselves, like the whole universe, which we imitate and follow through all time, being born and living now in our present manner and in that other epoch in the other manner. — Plato, Statesman, 274b, translated by Fowler
To see our condition in that way is sharply different from the story of our relation to a Creator who can spare us from evil if he wills it. We are given the choice to follow the way of the righteous and that is the possibility of our happiness as expressed in Psalm 1. But we need more help than that to overcome what confronts us. It is in that register I hear Paul saying that he needs help in his struggle with sin. The Creator as a participant in our person.
I could say more but figure I shouldn't bring too many points forward at a time.