Deuteronomy 32:8–9 (Qumran/LXX) Elyon apportions nations among divine sons, with Yahweh receiving Jacob - Yahweh one of El's sons (Masoretic fixes this). Kuntillet ʿAjrud, c. 800 BCE, blesses by "Yahweh of Samaria and his asherah" and "Yahweh of Teman and his asherah" -- i.e. plural localized Yahwehs, exactly how Near Eastern polytheism works. Psalm 82, God sentencing other gods to die like men.A flat denial of other gods arrives only with Deutero-Isaiah (44:6, 45:5–7), i.e., post-Persia.

I'd add a few things to your a-b-c list.

First, Mesopotamian and Egyptian summodeism: Marduk in Enūma Elish, the Ramesside Amun hymns. Akhenaten radicalized this trend.

Second, and this is unappreciated, soooooooo much of the faith passes through Greek[2] - Xenophanes "one god, greatest among gods and men," then Plato, Aristotle's unmoved mover, Stoics. Divine simplicity, immutability, omniscience, creation ex nihilo. Philo fuses all this crap, and Origen, Maimonides, Aquinas all run through Philo.

[0] "Refer to" aka with all the late-19th Century European baggage of what a "people" or a "nation" actually is.

[1] Note that even in the Bible, many centuries later, the prophets always come down from the hills into the cities, and once in the population center they generally yell at people and get yelled at. Solomon, as in biblical Solomon, built loads of temples to other gods, and it's extremely likely that the big temple - THE Temple, capitalized - was a multi-cult site. Good luck studyin any of this in the academy - I've known professional archaeologists who have changed their university rather than dip a little toe in biblical archaeology, due to how fraught everything is, and how nasty it gets very quickly.

[2] Unsurprising, since the foundational texts actually get written down in the Hellenic period. But I would argue even further than that, and would posit that the Hellenic period is the birth of the faith proper, where all the threads come together. Judaism and Christianity aren't parent and child, but more like a pair of siblings, with the latter child being something of a caboose baby. Although one could argue Islam would be the true caboose baby.

In reality many human societies throughout the ages have been monotheists.

On Persian influence: Demons are probably more directly Babylonian than Persian. Judah got that exposure during the Exile itself, not under Persian rule. Lilith (Isaiah 34:14) is the Mesopotamian Lilitu, and Babylonian demonology (Lamashtu, Pazuzu, the utukku) was already rich on its own. Where Zoroastrian influence is a stronger case is angels as named individuals with defined roles (Michael, Gabriel, hierarchies), which show up for the first time in post-exilic texts like Daniel, plausibly modeled on the Amesha Spentas and Yazatas after contact with Achaemenid Persia. Same goes for full cosmic dualism, a Satan as an independent adversarial being rather than a role in the divine court (as in Job or Zechariah, where "satan" is a title, not a name).

It's a big topic on its own, deserving separate treatment. I deliberately scoped this piece to the older, pre-exilic layer (the El/YHWH merger through Josiah's reform).

For what it's worth, the piece isn't arguing for a single external source anyway: Canaanite (El, Baal, Asherah), Mesopotamian (the Flood mirrors Atrahasis/Gilgamesh, the creation account echoes the Enuma Elish, plus the exile-era demonology above), Egyptian, and later Persian and Hellenistic layers all leave fingerprints at different points. Judaism's formation looks less like one merger and more like several centuries of absorbing and reworking whatever was around.