I think I tend to agree with the conclusion—namely that it was predominantly a Jewish influence on Christology. Part of my opinion is shaped by changes in and around the First Century in Judaism which, ultimately, culminated in the Masoretic Text evicting certain parts of the text that could remotely suggest anything akin to polytheism. Deuteronomy 32 is particularly one of the most affected chapters, but curiously "two powers" theology was largely left intact.

This is a particularly interesting period in Christianity, because you had numerous influences (including what would later become gnosticism around the same time), the term "trinity" wouldn't appear in extant works until sometime in the Second Century, then the Council of Nicaea in or around the latter half of the Fourth Century establishing it as doctrine.

So, I think the evidence of a decidedly Jewish influence is quite strong and would date at least to the Babylonian captivity.

I believe Dr. Robert Alter leans toward an evolution from polytheism -> monotheism in Jewish thinking (I highly recommend his The Hebrew Bible: A Translation with Commentary); but I think the evidence for a sort of henotheism is a bit stronger and more sensible, which would better fit the sources you shared here, alongside the biblical texts.