Drew, you made many good points - excellent post!
The pope is then no longer the servant of revealed truth but becomes the revealer. It is a bizarre new religion that believes in an empty office that never can and never will be filled.
I think most sedevacantists take it even further than this, because to them, he is not merely the revealer, oh no, he is much more than that because whatever he says, no matter what he says, is made an infallible truth upon his utterance - the same is said as regards the hierarchy misnamed; "the magisterium." This takes him from being the Revealer to being the Instituter - but this Instituter is somehow, something less than God yet is, as you say, still their rule of faith.
They also imagine that when the hierarchy all teach the same things, no matter what the teachings are, those current hierarchical teachings, by virtue of present unanimity, have met the requirement for protection from error by the Holy Ghost and as such, those teachings are infallible. To most (all?) sedevacantists, this insane formula is de fide.
If they actually had any faith whatsoever in this belief which they argue is de fide, (which incidentally, this same belief is shared by the conciliarists), then they are bound to "submit" to them, but since they know those teachings are wrong, and they know the hierarchy is wrong, instead of realizing their belief cannot be right, and instead of searching for the truth of the matter, they cling to their belief at the expense of the entire hierarchy, particularly the pope.
Have you ever asked a Sedevacantist exactly where and when the pope lost the office? You’ll never get the same answer twice. Probably not even from the same person.
I can rarely get sedevacantists to answer clear questions with clear answers. Dozens of times I've asked sedevacantists why they personally, even need a pope at all - having received only one honest answer in like 2 years convinced me there is a lot of pride involved.
My theory about all of this is that, like the conciliarists who "blindly obey" the pope, the sedevacantists embrace those false teachings which originate from some of those "well respected" 20th century theologians who teach that even in his non-infallible teachings, a pope cannot harm the faithful.
I believe these erroneous teachings of those "well respected" 20th century theologians were accepted as authentic "Church teachings" and were, as +ABL has said, "infiltrated into the seminaries, the catechisms and all the manifestations of the Church" in the late 19th and through the 20th century.
I don't know how to prove such a theory but if correct, it offers a sound explanation as to why, in the 1960s, multitudes not only freely abandoned the only faith they ever knew and knew it to be absolutely true and wholly necessary, it also explains why they "stuck with the pope" and went along with the pope into the NO - of their own free will.