I described myself as an advanced libertarian.
As for books about the Peace of Westphalia, you might try “The Myth of the Free Market: The Role of the State in a Capitalist Economy” by Mark Anthony Martinez. I haven’t read it, but just scanning through it I found it insightful and agreeable. (At least, around the Peace of Westphalia.)
It seems to be aimed at people like libertarians who oppose the idea of the state, and reviews suggest it has plenty of references.
Not having actually read it, I can’t vouch for its opinions, but my own education came from a number of sources, none of which I entirely agreed with. It should at least give you a starting point.
There’s also a blog/web site for it, which I haven’t actually done more than glance through.