With regard to the Bishop Sanborn quotation, as I told you, I am not an R&Rer. I agree with his criticism of R&R. Again, I have to repeat that I DO ACTUALLY THINK that the Holy See is most likely vacant. But the operative word in that previous sentence is "I". I am using my private judgment to determine that various statements in Vatican II contradict Tradition. But, quite honestly, if I held the same views as Bishop Sanborn regarding EENS, then I would have to say that Vatican II does NOT contradict Tradition. But that's a side issue.
I don't understand what's so difficult about this.
No notion that pops into my head other than anything that's already been clearly defined by the Church can possibly have the certainty of faith. Most SVs can point to about 5 or 6 different statements in Vatican II that they classify as heretical or erroneous. But I have also seen other people reconcile these statements with Traditional Catholic teaching. SVs can point to the New Mass, but if you look at their "Anaphora I", in Latin, it's almost verbatim the Roman Canon. I've seen the Novus Ordo Missae offered in Latin, with the priest facing the tabernacle, with Gregorian chant, with people receiving Communion on the tongue / kneeling, with the ladies wearing veils, and suddenly the judgment about whether the NOM intrinsically harms the Faith becomes a little less black & white (than say when you're talking about the proverbial "Clown Mass"). In fact, you'll find that Pius XII foreshadowed a number of the changes in the NOM with some of the Holy Week changes. Sometimes Francis says heretical-sounding things, but at other times he speaks with great devotion about Our Blessed Mother, the Sacred Heart of Jesus, the Blessed Sacrament, or his devotion to certain saints. There are a lot of judgment calls. There's enough here to create a very strong positive doubt about what's going on. But NONE of these judgments rise to the level of having the certainty of faith about them.
Nor, in the end, is it de fide, by the way, that a heretical pope would lose office ipso facto.