1. Exact quote from Fiona herself "I might be the first Warden who does not have to go on the Calling." Notice that "might" is towards doubting being the first not being free of the taint. She has cured the taint but we don't know if she is the first. One thing is certain and she will never go to any calling.
2. We haven't met any stronger unpossessed mage, yet. The way The calling and Asunder describes her magic she is one of the strongest of not the strongest.
3. See? This is what I'm talking about. Many circles revolted before Fiona actually got the vote to separate. She is doing the majority want. Its as moral as it gets.
4. Which is why I said I an be wrong be the signs of author's favor are there unless inquisition changes that.
1. Assumption, and it could many things, she could have been planning to hang herself if her egomania wasn't satisfied.
2. I am of a mind with the Others, there have been many powerful mages presented, and her own skillset isn't very highlighted so again assumption.
3. Only one notable rebellion occurred post kirkwall and it was put down fairly quickly. So again conjecture and debatable.
4. I doubt it will, Gaider doesn't really play favorites.