It's often hard to tell ancient history apart from fantasy.

"Sargon the Great" was a real historical figure

there was a pretty long discussion on this topic some time ago on the regular mw page i think. that is a good spot, i read the books when they originally came out and didn't start mw until about 2005 so i had totally forgot the connection.

there are some really good points on the topic in this thread on the overall 'syncretism' of the es series, which is a nice way to say borrowing symbols and ideas from existing sources. Bal was I believe a god of Assaryian and/or Babylonians (and later the Phoenecians) and became equated with Satan and all things bad in early Jewish history and writing because those cultures were enemies of the early Jewish people. Basically, there is nothing new under the sun.