I see that you are still struggling with the idea of calling possible beings as “potencies.” Yet I pointed to you a text from the Summa which shows that even St. Thomas referred to possible beings as “in potentiality” toward existence. He said, “Those things that are not actual that means, possible beings] are true in so far as they are in potentiality; for it is true that they are in potentiality; and as such they are known by God” (ST, Part 1, Q.14, Art. 9, Reply to Obj. 1. [The phrase in parenthesis is mine, inserted for clarity.]
Maybe the following will help to clarify this further. Consider the term “being.” Strictly speaking, the only thing that we can properly call a being is something that exists; that means, a real being. Yet, we also apply the term “being” even to non-real or fictional beings, such as a mermaid or a centaur. Since these are not real beings, and exist only in our minds, we call them by a special term: “beings of reason” (or entia rationis).
In like manner, the only thing that we can properly call a potency is the potency that we find in actual subjects (such as the prime matter of existing bodily substances, or the essence of immaterial substances). This potency is referred to as subjective potency and is found only in created things, as you pointed out. In a less proper sense, however, we may apply the term “potency” to the potency of possible beings toward existence, which St. Thomas has also done. But since this potency is not found in an actual subject, but in things that are mere objects of God’s Power or God’s Mind, we call it by a special term: “objective potency.”
If we can call a being of reason a “being” even if it is not a real being, then why can’t I call the potency (toward existence) of a possible being a “potency” even if it is not in an existing created being? St. Thomas did not hesitate to call it that, did he?
This manner of handling terms is really not uncommon in philosophy and the other sciences. In human language we use terms sometimes in a broad (or wide) sense, sometimes in a restricted (or narrow) sense. We use terms sometimes strictly, sometimes loosely. We use terms sometimes properly, and sometimes less properly. I don’t find any problem with this, as long as we clarify in what sense we are using a term. Consider, for example, the term “change.” Strictly speaking, the only kind of transition that we can properly call a “change” is one in which there is something that changes; that means, one where there is a subject or substratum of change. But in this thread we have used the term “change” loosely to refer to any kind of transition whatever from one state or thing to another. If this loose sense is adopted, then creation may be referred to as a “change” from non-being to being. But if we use the term “change” in its strict philosophical meaning, then creation is not a change at all because there is no subject that changes. Rather, there is a production of the entire being of a thing from nothing.