The Magisterium, the sacred teaching office of the Church, was not exercised in any incident that you mention. In fact, it is exercised when a judgment is given to the whole Church by the Pontiff, a Council confirmed by the Pontiff, or the ordinary universal magisterium, in which case it is binding upon all and cannot be debated (see Pius XII, Humani generis 18-21, Bl. Pius IX, Tuas Libenter).
Was the Holy Spirit present when the Magisterium claimed the Jews no longer need convert to be saved?
Since it has never claimed this, no. He was, however, present when the Magisterium condemned this thesis of no Jewish conversion: "it would be contrary to the faith to consider the Church as one way of salvation alongside those constituted by the other religions, seen as complementary to the Church or substantially equivalent to her ... followers of other religions ... are in a gravely deficient situation in comparison with those who, in the Church, have the fullness of the means of salvation." (Dominus Iesus 21-22).
Right, the fine line between material and formal heresy. Talk a good game on paper then do what you like in practice.
These guys are good. The modernism is difficult to detect even for the pros.
BTW, those weren't strawmen. Those were actual questions which you conveniently sidestepped. The point is, THE MAGISTERIUM NO LONGER HOLDS TO THE CATHOLIC FAITH. What will it take to get through to you? Will Antichrist himself show up and find a supporter in you because "the Magisterium can never err?"
But novelties are not magisterial teachings. The Pope is not acting as a magisterial teacher when he proposes what is novel. Only when his teachings adhere to the consistent teaching of the Church can his doctrines be said to be binding. It doesn't matter how many pontifical institutes declare, for instance, that Jews need not be converted to Christ, this is not binding in any way, shape or form.
What it is, though, is destructive of the true doctrine--which is deliberately ignored and subverted and allowed to be forgotten. So it goes with most Church doctrines of the past which now languish in neglect. There is no need therefore for any direct assault on doctrinal truths either. It is enough to just suppress and subvert dogmatic truths and to create an environment for the breakdown of the Catholic faith itself.