Hey everyone, I think I answered my own question through some searching last night, and wanted to share my results.

Of course, the Book of Esther can't be used as a historical fact, much like any religious source. In fact, it is debated whether the Persian king in the Book is actually Xerses... Some translate it to Antexerxes, and etc. However, it is widely accepted that Xerxes is the King being portrayed.

While it isn't face, the Book of Esther can be used to study that time period much like any other fiction book written at the time. It gives us an insight on the Jew's of Persia's perception of Xerxes. This view differs from that of Herodotus, and of course the 300 reincarnation. He is perceived as more just and merciful than the barbaric nature Herodotus provides.

In regards to my second question... I'm still really not sure. Could they have read the book of Esther and seen him as someone who sings about a tree and admires it's beauty? Maybe. That is something I'm not sure on.

I could be all wrong, of course. If Esther was to be used at all, I think it would have to be how Xerxes is perceived by the Jewish.