Can you tell me the story of Pharaoh ruling over the city of Nineveh & its source?

A hint to the idea that Pharaoh did not die at the splitting of the Reed Sea can be found in Exodus 14:28. The verse states that the water covered over the Egyptians, “v’lo nish’ar bahem od echad.” The plain meaning of this verse is that not even one person remained. The Midrash, in Pirkei D’Rabbi Eliezer, says that the verse can be read to mean “up until, but not including one person (i.e. Pharoah), was left.” The Midrash continues to note that Pharoah became king of Nineveh.

Additionally, the commentary Ba’al Ha’turim points points out the following linguistic similarity: In Exodus 14:31 it says, “...And they [the Jewish people] believed in the Lord…”; and in Jonah 3:5 it says, “And the people of Nineveh believed in G-d….” Both verses use the word “Va’yaminu”—and they believed. This points us to the Midrash quoted above, and explains that the people of Nineveh were brought to belief in G-d by Pharaoh, when he told them of the wonders that occurred in Egypt and in the Red Sea.

The implications of this Midrash are truly astounding! The fact that someone like Pharoah, who time and again refused to recognize the power of G-d, could repent and teach a whole city about the truth of G-d, is a remarkable lesson in the strength of repentance.