-did Paul actually write Romans 13:1-7 or was it added later, for understandable reasons?
I don't think there's any debate about the Pauline authorship of Romans substantially as it presently exists, but I'm open to being corrected.
I'm not sure there's any way of knowing, but again, I'm open to being corrected.
A lot of what's taken for granted about Christian theology on a really basic level was developed from Paul's writings; not only some of the specific flash-point topics that might immediately come to mind, on many of which it can be argued that Paul has been tendentiously interpreted or had less than complete knowledge of the subject (although he still needs to be taken seriously in these areas because they're often more central to the broader points that he's making than one might like to believe), but stuff like the nature of Jesus' divinity, development of the concept of the extent of the apostolic commission beyond the original apostles, development of the idea of Christian life in the world and the establishment of the Church as a community--which we also see Paul heavily involved with in Acts, the final decision that Christianity was to be a catholic religion like Buddhism or the Mithraic Mysteries rather than a type of evangelistic Judaism, and a lot of the discussion of virtue or the Virtues.
Paul in general uses a great number of athletic and military metaphors. It's genuinely difficult to reconcile elements of his writings to a pacifist Christian understanding (although I would obviously submit that such is a worthwhile effort), but off the top of my head there are aspects of the sixth chapter of Ephesians, whose authorship is admittedly the subject of more dispute than that of Romans, that seem to at the very least modify some of what's said in the passage we're discussing.
