Why does my relationship with the pope suffer when I defend myself, in my own province, from invading armies?

Why are other factions allowed to attack me, seemingly without any sanction from the pope?

Why am I rated as 'very untrustworthy' despite never having broken a treaty or even starting a war?

Why have the last 2 papal elections been won by a cardinal with less votes than the guy I voted for?

Why did I pay good money for this game because it's really starting to get me down?