1. Garry Wills, Papal Sin.
2. He had-essentially made these concepts part of his Magisterium. What he wrote was NOT dogma but a guide to thinking and studying Dogma. That is the province of individuals, not the Dogma of the Church. That is like trying to make Fatima or other private revelation Dogma. It may sound good to the pious but it would be against Dogma to do so. This, by the way, disproves the whole concept of infallibility. Dogma is about Credal issues. Papal authority over dogma is not credal nor particularly doctrinal because the Doctors of the Church are not that stupid. 
3. Christ built the first community on Peter's shoulders and if Constantine had been thinking clearly, he would have taken the bishop of Rome with him to the new imperial see and called him the heir to Peter. He might have, actually. You won;t get an honest answer on that out of the Vatican.
4. Obscure
5. Then find it. I think I did. It was about strategy, not natural law.