"the Pope and the bishops in communion with him".
That means that the Magisterium of which we speak, is an authority which is shared by the popes (whether they be bad, good, frail, robust, theological geniuses, theological retards, etc.)--- and the bishops in communion with him. It is is not the personal characteristic of one man and his particular talents.
"charism of infallibility"
This is not a positive charism ("he'll always say the right thing, at the right time, in the right way") but a negative one (he will be prevented from saying anything that could lead the whole Church into error.) It is not a license: it's a limit.
Obviously everything a Pope says cannot be infallible. Let me give some examples of when this charism is not in play:
That last one in particular means that when Pope Benedict writes and publishes a book during his pontificate, e.g. "Jesus of Nazareth: The Infancy Narratives" (2012), or when Pope Francis gets interviewed on an airplane, or writes a letter to the editor of La Repubblica, it's of great interest to the faithful (and the infidels as well, I suppose) but it is not dogma per se and not infallible.
And when you quoted Para 100 of the Catechism, why did you inexplicably cut off the last eight words of the relevant sentence?
100 The task of interpreting the Word of God authentically has been entrusted solely to the Magisterium of the Church, that is, to the Pope and to the bishops in communion with him.
Who do you think you are, Reuters?
Mine at 53.