About the Pope not being able to go to war....
The first should suffice, but if you need to be assured I've taken Rome in the one labeled Papal Apocalypse. This happened just after I completed two of the three UHVs as Arabia.
Don't know if this was already mentioned or is supposed to happen, but I figured it was new to me and I'd put it up just in case.
Who declared the war? Did you declare war on the Pope or the Pope on you? (I found one more Papal war bug that will be fixed in the next version)
I can confirm that the barbarians are at peace by default now. As a result I had Kiev winning a historical victory in my French game.
I met a CTD while playing as France; I'll see if I can find the Autosave and re-create it.
I can't recreate it, so chalk it down to a sporadic bug.