I have a question about all the words below for leader/emperor.
If I wanted to write a story about the Plagues of Egypt, which word would I use for “Pharaoh”?
That depends on your purpose for the translation. For some audiences, it might be appropriate to transliterate "Pharaoh" and explain it in a footnote. For others, perhaps {ta'} or {voDleH} is enough.
I asked and made sure - it’s a title, not a name. Same with writing a story about Esther, and there is King Xerxes. (I will be using the longer name that starts with A instead of Xerxes though - it is easier to write in Klingon!)
Ahasuerus? Why not go with the Old Persian original Xšayaṛša (maybe *{'IHSayarSa} or something like that)?