Do you have a source for your “every Roman Catholic is supposed to be taught and know the parts of Mass in Latin” statement? My pastor, who is in his 60’s, said he had no Latin at the seminary level, and it’s difficult to believe that a Latin learning expectation is present for the laity, the vast majority of whom will only experience the Ordinary Form.
The documents you ask about may be found here:
liturgyoffice.org.uk/Resources/Music/Jubilate/
The Holy See has indeed insisted over the years about the importance of the faithful being able to sing the common parts of the Mass in Latin, especially on account of gatherings of the faithful from various countries having different languages – as with the Holy Year of 1975, for example. And the Holy See, as a practical help, issued a booklet personally sent to every bishop by Blessed Pope Paul VI.
In my personal experience, the faithful of Europe and Africa do well in singing the Mass parts that are in Latin at Masses of the Holy Father, above all when assisted by the choir and when the Mass responses are taken from Mass VIII (the one familiarly known as The Mass of the Angels). From what I have seen over the years, though, I personally am dubious as to how well the directive was actually implemented in North America where, regrettably, even the requirement for seminarians to study Latin was not always complied with in years past.
Regarding the requirement that “Pastors of souls should take care that besides the vernacular ‘the faithful may also be able to say or sing together in Latin those parts of the Ordinary of the Mass which pertain to them’” I have gathered that the necessity of recourse to Latin as a common liturgical language was not as frequently a real and necessary prospect in North America as it was in Europe.
Note the post conciliar document Musicam Sacram, which makes explicit as a duty what Sacrosanctum Concilium called for. A relevant passage may be found here in paragraph 47:
*47. According to the Constitution on the Liturgy, “the use of the Latin language, with due respect to particular law, is to be preserved in the Latin rites.”
However, since “the use of the vernacular may frequently be of great advantage to the people” “it is for the competent territorial ecclesiastical authority to decide whether, and to what extent, the vernacular language is to be used. Its decrees have to be approved, that is, confirmed by the Apostolic See.”
/…/
Pastors of souls should take care that besides the vernacular “the faithful may also be able to say or sing together in Latin those parts of the Ordinary of the Mass which pertain to them.”*
adoremus.org/MusicamSacram.html