18 out of 29 Ayah here are directly from targum Sheni. Only 11 original Ayah and it was to add credibility to Islam!
The above was according to this book: Avanzini, Alessandra (2016). By land and by sea: a history of South Arabia before Islam recounted from inscriptions. L'Erma Di Bretschneider. Which goes through all of the various Axumite and Sabaic texts. It's available on Academia,edu for free.
Now who did worship the Sun in south Arabia was the Himyarite Kingdom with the worship of Shams (a Sun goddess, the later wife of Almaqah) in the temple at Sana'a. This however did not start in Arabia until the 2nd century BC and continued until the 6th century AD (Although the kingdom converted to Judaism/Christianity before its end in 6th century AD, they also worshipped Ar-Rahman btw who is a pagan god).
So, the southern kingdom Mohammad would have been thinking of (if any at all) who have been what the current people worshipped of his day, which is evidence that the Qur'an is man-made. It gets the facts wrong but uses what seems to be true from the time period of Mohammad. It does this a lot. So, the Qur'an only has the information that Mohammad had access to and gets everything else wrong.
So, what does that mean? The Qur'an gets the religion of Sheba wrong. Instead of describing the actual Iron Age cult of Almaqah, it projects later Arabian sun-worship (well-known in Muhammad's own day) back into the distant past. That is exactly what you'd expect if Muhammad were drawing on oral folklore; not what you'd expect if this were the eternal, error-free speech of God.
Second, this isn't an actual problem but there are many problems with the Quran's version of Pharaoh. First off, you are overstating what scholars actually say. The term Pharaoh was not invented in 1550BC. What they say is that before the New Kingdom (18th Dynasty, ca. 1550 BCE), per-aa ("great house") referred to the royal palace or institution, not directly to the king. Over time, the term came to mean the ruler himself. That's not the same thing as saying, "Pharaoh was never used for rulers before 1550." The shift was gradual, and even in later texts "king" (nsw) was the primary formal title, while "Pharaoh" was more of an epithet.
The Biblical writers naturally used the word Pharaoh because that's what their audience understood for an Egyptian ruler. That's like calling Nebuchadnezzar a "king" in English, even though the Akkadian word was sarru. Translators don't try to preserve historical linguistic precision; they try to relate truth to their audience in a way they understand.
You are right, the Qur'an does use king of Egypt for Joseph and Pharaoh for Moses, but this isn't original to the Quran. The Jewish Midrash on Genesis and Exodus uses "king" for Joseph's time (kinda like Surah 27 copying from Targum Sheni) and later rabbinic texts distinguish between "kings" in patriarchal times and "Pharaoh" in the Exodus narrative. So, Mohammad could have easily just picked this up from the Jews the same way he did all their other folklore.
Not to mention the NUMEROUS historical problems with Pharaoh. Such as Haman serving in his court (hundreds of years before Persia existed), him using crucifixion (a thousand years before it existed), him having a stone 'ark' for Moses as a baby in the Nile (stone can't float), the Israelites never fought a war against Egypt, the Qur'an says there was only one Pharaoh when there was two during the lifetime of Moses (we know which two Pharaoh's it was too - Tutmose III and Amenhotep II), Haman and Pharaoh didn't build the tower of Babel, etc.
These are anachronisms much worse than the Bible's supposed "error". Especially the Haman and crucifixion errors. Those can't be circumvented. The Qur'an is full of thousands of historical and cultural errors.
Again, you assume that we need an Isnad chain to have evidence of him copying, that is nonsense, and no serious scholar would take that claim seriously. It is circular reasoning and a logical fallacy. You are saying that the Qur'an defines X which proves Y but how you justify Y is X. This is obviously an error in logic. You are using the Qur'an to define what is true then say it's true because it lines up with the Quran. That isn't how we do history or truth. For something to be true it needs external evidence to support it, which the Qur'an doesn't have.
"Share the reference of Jewish Midrash where it says that Joseph met the King" - Genesis Rabbah 88:2 (4th century, the Qur'an quotes from Genesis Rabbah a lot so the author likely had a copy; such as Surah 21:51-70 and, 37:83-98 about Abraham smashing idols which comes from Genesis Rabbah 38:13, Surah 2:31-33 and Genesis Rabbah, 17:4 with the conversation between God and the angels about knowing the names of animals, etc), Midrash Tehillim 105:6 (7th century), Mishnah Sotah 1:9 (2nd century, its gemara is in Sotah 10b, Berakhot 55b). So it would have been popular, and we know he copied from sources which did such a thing on other matters because like 15-30% of the Qur'an is from the Talmud.