See, I agree with the part about corporations being their own sort of government. It's something I think most libertarians just don't get.
That said, there will be corporations. Working together makes things possible that wouldn't be solo, which is why massive corporations generally stomp mom & pop businesses. Anyone who chooses not to join a collective will eventually lose out to the people who do form collectives.
As for central government becoming nation-states... you do realize that nation-states spend most of their time on war right? Nazi Germany was a nation state. It's all about warlords and territory at that point, which is not a recipe for anyone's freedom.
EDIT: Still planning to reply to your other long post, just haven't had time.