So I've refined my thesis a bit: "Milton channels his own views and personality into Satan in order to create a more human version of the devil as opposed to the previous versions of the devil in christian literature. Milton creates this new form of Satan in order to make a political statement on the monarchy in the Church."
I'll tweak it more as I do some more research but that's the basic idea. As for research, I need to look up other versions of the devil in Christian literature to compare to Milton's Satan. I could probably use the devil from Doctor Faustus. I could probably even use the Bible for that as well. I also need to do research on some of the political issues Milton was fighting against during the time he was writing Paradise Lost, particularly on his feelings on the politics in the Church. If you guys happen to find anything related to that, let me know.