What is the source of the 44 assertions made in the Creed of Athanasius?

I question the whole assumption of the OP. It's simply not possible to limit any statement of belief to the text alone. It never has been. This is not a criticism of statements of belief. They can be true, and useful. But by simple definition they must stand outside the Biblical text because they are answering the question, "This is what I believe about the Bible's text."

To put it another way, for any text there is a difference between the text and its meaning. They are not the same thing. The moment two people have differences of opinion about the meaning of a text, the text by itself becomes insufficient to resolve the difference. We need to go beyond the bare text to the question of interpretation.

Consider the classic example of John 1.1, as quoted in the OP. One person may say, "The Word was God." Another person may say, "The Word was a god." Both people have accepted the truth of John 1.1. But at the same time the text of John 1.1 means different things to each of them. How do we decide which is more correct? Answer: by offering evidence from outside that single verse to support our view. We can't just quote the verse as evidence of the meaning of the verse; that would be a circular argument.

So we can ask of the Athanasian creed, why did its framers believe those statements to be true? That is a valid historical question. And you can ask, is its content a consistent and reasonable interpretation of the Biblical text? That's a valid theological question. But you can't ask, why didn't they just quote the Bible verses? If that were possible, we would have had those verses in the creed from the beginning.

As you noted in your question, Scriptures can be adduced to support any number of inferences and doctrines. So it stands to reason that true teaching must consist of more than the mere having or pointing to the Scriptures, but rightly understanding them; it also stands to reason that rightly understanding them consists in more than personal assurance or ability to convince other of one's interpretation—which can in theory be accomplished by heretics (no matter according to whom they would be heretics). Therefore, you must adduce Scripture to prove your case only if your case is demonstrably the Christian faith apart from the Scriptures (else we fall into relying on our private interpretation or the might of our arguing for an interpretation that neither we can be sure is true, nor those convinced): that is, you must be able to demonstrate that you are presenting an interpretation of the Scriptures in line with that "faith" once delivered to the Church, and not something novel.

It's for this reason that St. Athanasius wrote things like:

But, beyond these sayings [of Scripture], let us look at the very tradition, teaching, and faith of the Catholic Church from the beginning, which the Lord gave, the Apostles preached and the Fathers kept.¹

But after him and with him are all inventors of unlawful heresies, who indeed refer to the Scriptures, but do not hold such opinions as the saints have handed down, and receiving them as the traditions of men, err, because they do not rightly know them nor their power.²

But since they allege the divine oracles [Scripture] and force on them a misinterpretation, according to their private sense, it becomes necessary to meet them just so far as to vindicate these passages, and to show that they bear an orthodox sense, and that our opponents are in error ...³

As you can see, the chief defender of orthodoxy at the time (nor anyone at the time, for that matter), was no 'sola scripturist' (find it in the Bible or it's not Christian teaching). When engaging in apologetics using Scripture, you must vindicate the passage against blatant misinterpretation, yet never by doing so implying the truth, and the true meaning, is arrived at purely by a debate between men. We must also appeal to unchangable Tradition to verify and vindicate our own interpretation, not simply cite our own, so proving that it is not at odds with the deposit of faith given by the Apostles.

Hence, Athanasius doesn't make it simply a back and forth of 'who has the best interpretation' but rather is famous for the statement, "how many Fathers can ye assign to your phrases [i.e. novel interpretations of Scripture]?"⁴

Therefore the standard that all true expounding on the meaning and true sense of Scripture must be yet another Scripture ("I cannot locate where any of the 44 assertions made in the Creed of Athanasius are also made in the canonical scriptures") is not only virtually impossible, but not the mode of the Church—and never has been. Ironically, such a doctrine itself is not found in any Scripture passage!

Rather, the orthodox sense of Scripture is enumerated in various Creeds, each having a different focus and purpose (e.g. the Nicene as useful in combating Arianism, the Constantinopolitan as useful in combating the Macedonian heresy, the Athanasian against misrepresentations of the Trinity, etc.) by their being the true teaching of Scripture.

That said, there are of course Scriptural proofs for each one, if not single 'proof texts.' (What you can prove from Scripture is only as good as your ability to prove your interpretation is infallibly what was handed on and intended by the Apostles.) But since you said you are not interested in such, I'll omit them.

^{1 To Serapion 1:28 (after citing biblical passages concerning the deity of the Holy Spirit)}

^{2 Festal Letter 2:6}

^{3 Discourse Against the Arians 1:37}

^{3 De Decretis 27}

The simple answer to the question, How many statements arise from the Bible? There are NONE. The reason is simple - creeds by their very nature are a summary of conclusions based on (supposedly) Biblical evidence. Therefore, their language will NOT be that of the Bible but of the terminus of theological logic.

There are a very few phrases that arise from Scripture such as "judge the quick and the dead" (2 Tim 4:1, 1 Peter 4:5, Acts 10:42). Another might be, "give account of their own works" (Rom 14:12, 1 Peter 4:5, Matt 12;36, etc), and one or two more. But phrases do not make a sentence nor thought.

But more importantly, there are many unscriptural words such as, "trinity", "uncreated", "unbegotten", "coequal", "almighties", "coeternal", "eternals", etc. This precludes most of the material arising from the Bible.

So let us be quite clear - the Athanasian creed is a creed (summary of belief) and is of dubious and unknown origin; it is a man-made document; it is a summary of some theologian's thoughts and conclusions. It makes only vague references to the Bible. It also makes no pretense at being of direct Biblical origin.

This does not make it right or wrong - it just makes any connection to the Bible rather indirect. Any link a creed has to the Bible will always be logical (ie via logic and reason) rather than lexical and linguistic.