I like how St. Francis de Sales explained it. Think of a king who passes laws. Not everything he says and does is therefore the law of the land, but only those things intended to be laid down as laws for the land. Analogously, the Pope is infallible when he is laying down the “law of belief” or the moral law for the whole Church, but not in his other sayings and actions.
Only the Immaculate Conception and the Assumption are infallible Ex Cathedra Magisterial declarations.
Says who? This would means an ecumenical Council dealt with this issue when there was only one instance of it. It would also mean St. Francis de Sales dealt with this issue when there were no instances of it. That doesn’t pass the common sense test.
At the First Vatican Council, some bishops wanted to define some sort of procedure the Pope would have to follow. The relator (a bishop responsible for giving official explanations of concilliar texts to the Council) responded that this could not be done because various procedures were used in the past:
Bishop Gasser:
But, most eminent and reverend fathers, this proposal simply cannot be accepted because we are not dealing with something new here. Already thousands and thousands of dogmatic judgments have gone forth from the Apostolic See; where is the law which prescribed the form to be observed in such judgments?
Granted, he is probably speaking hyperbolically, but in any event it is obvious he had more than one in mind. Throughout history Popes have often intervened to provide definitive judgments in the areas of faith and morals, sometimes definitively condemning long lists of propositions (e.g. Coelestis Pastor of Bl. Innocent XI, Ex Omnibus Afflictionibus of St. Pius V, Unigenitus of Clement VI, etc., etc.; each condemned proposition is probably considered an individual judgment by Gasser above accounting for the high number he gives) and sometimes definitively asserting a truth (e.g. Benedictus Deus of Benedict XII, Unam Sanctam of Boniface VIII, the dogmatic letter of St. Agatho, etc.).
I am also not sure your assessment of the definitive judgments in Humanae Vitae and Ordinatio Sacerdotalis are accurate, since they were definitive judgments that bound the whole Church–why would they not be instances of papal infallibility? Regarding Humanae Vitae, Fr. Ermenegildo Lio, who advised Pope Paul VI on it, wrote a book about why it was indeed intended as an ex cathedra judgment by the Pope and this book received a commendation from Bl. John Paul II. I have not seen anyone refute his argument (especially not anyone as close to the source). The idea that it was not ex cathedra seems to stem from a Vatican spokesman who said it was not when presenting it to the press, but his comment that it was not seems to have been unauthorized since it was deliberately ommitted from the official transcript late published.
Likewise, the wording in Ordinatio Sacerdotalis follows pretty much word for word the text of Lumen Gentium concerning papal infallibility and it has been confirmed as a definitive and universally binding judgment by the CDF on multiple occassions.
I also think, in terms of recent examples, the definitive declarations of Bl. John Paul II explicitly and formulaically invoking the authority of St. Peter to condemn the murder of innocents, abortion, and euthanasia in Evangelium Vitae qualify.
Remember too, just because a doctrine is taught infalllibly one way, does not mean it is not also taught infallibly other ways concurrently. It can be taught by the universal belief of the entire Church (inlcuding the laity), the universal ordinay magisterium, the definitive judgment of the worldwide episcopate, the definitive judgment of an ecumenical Council, and the definitive judgment of the Pope. The Church is constantly reiterating the truth by these means.
The idea that there have only been two instances of papal infallibility is incredibly new and I am not sure where it comes from. Even those with the most limited view of papal infallibility at the time of the First Vatican Council (like Bl. John Henry Newman) did not make this claim.
