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Yes, God has, and this principle derives from the indefectibility of the Church's Magisterium.

No, God has not. You know not what you are talking about here. The pope is safeguarded from the possibility of error when he defines a doctrine concerning faith or morals ex cathedra, this is what was defined at V1. This is the teaching of the Church, this is the papal infallibility we learned from V1, this is what we are bound to believe.

As V1 taught; among all the doctrines which we must believe, are those doctrines contained in the Church's Magisterium, some of which are defined ex cathedra, again, this teaching comes directly from V1. So to say "this principle derives from the indefectibility of the Church's Magisterium" only demonstrates a decided confusion in your thinking here.

1.  Pope speaks ex-cathedra (on faith and morals) = infallible.
2.  Pope speaks authoritatively (on faith and morals) but not ex-cathedra = infallible.
3.  Pope speaks authoritatively (but NOT on faith and morals) = not infallible because this is a governmental decision.
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I think most catholics would agree with 1-3 above.  Yet, Fenton goes further and teaches a #4.
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4.  Pope speaks non-authoritatively (on faith and morals) = infallible.
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This #4 theory effectively makes ex-cathedra statements pointless because the pope is infallible regardless.  This is ridiculous and as far as I can tell, Fenton is the only theologian who argues thus.

Catholic doctrine is not limited to what's been solemnly defined.  If souls could lose their faith by assenting to the Magisterium, then the Magisterium would have defected.  It's a simple correlative to the Church's overall indefectibility.

R&R claim that the Church's indefectibility lies solely in its material continuity, but the Church cannot defect in HER MISSION either.

From NewAdvent regarding the Church:

Among the prerogatives conferred on His Church by Christ is the gift of indefectibility. By this term is signified, not merely that the Church will persist to the end of time, but further, that it will preserve unimpaired its essential characteristics. The Church can never undergo any constitutional change which will make it, as a social organism, something different from what it was originally. It can never become corrupt in faith or in morals; nor can it ever lose the Apostolic hierarchy, or the sacraments through which Christ communicates grace to men. The gift of indefectibility is expressly promised to the Church by Christ, in the words in which He declares that the gates of hell shall not prevail against it. It is manifest that, could the storms which the Church encounters so shake it as to alter its essential characteristics and make it other than Christ intended it to be, the gates of hell, i.e. the powers of evil, would have prevailed. It is clear, too, that could the Church suffer substantial change, it would no longer be an instrument capable of accomplishing the work for which God called it in to being. He established it that it might be to all men the school of holiness. This it would cease to be if ever it could set up a false and corrupt moral standard.

Tell me with a straight face that the Conciliar Church is still essentially the Catholic Church, that is not become "corrupt in faith and morals" and has not "set up a false and corrupt moral standard".

Fenton says that non-infallible “directives” are protected by a special “charism”.  Ok, maybe.  
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The problem comes into play when you try to come up with a PRACTICAL EXAMPLE of this.
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1.  Name a time when the pope, in matters of faith and morals, directed/commanded (under pain of sin) a belief outside of an ex-cathedral statement.  I can’t think of any.  
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1b.  Isn’t what Fenton describing the use of the ordinary/infallibility of the pope?  That is, when JPII reiterated that it is of Tradition that women can never be priests. That sounds like a non-ex-cathedral directive and it is certainly infallible. 
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2.  The further problem is when one applies Fenton’s theory to V2, because 1) neither V2 nor the new mass were “directives” and 2) they have nothing to do with infallibility because neither were obligatory (ie thus, not directives).  
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So those claiming that this “special charism” applies to V2 (assuming Paul VI was a true pope) are wrong.  Even if Paul VI was legitimate, V2 doesn’t fulfill what Fenton was describing.