It has been said that no one may judge a pope because that is a thing proper to a superior, and he has no superior. But try this reasoning. God is his superior, and when a pope is in formal heresy he is judged by God who with divine law places the pope outside of the church, at the same time he ceases to be head of the church.

Correct.  When a man who claims to hold ecclesiastical office, including, and especially the papacy, teaches heresy and or engages in heretical acts, he shows himself to be judged already, by God.  Thence the man whose exterior words and actions we judge is not our judging the "pope" but our judging a man separated from the Catholic Church through heresy plain and simple.  A purported pope who becomes a heretic, loses his office (if he ever held it to begin with) by that very fact without any need for a declaration, though a declaration that declares what already has happened could be useful.  

The sin, culpability is judged by God, this pertains to his salvation or damnation.

The exterior act(s) is judged by faithful seeking to preserve their souls from error, this pertains to his ability to legitimately hold ecclesiastical office.  

A private formal heretic (he does not teach heresy or engage in heretical acts and therefore does not destroy the visibility and unity of the Church) can be a valid Pope that goes to Hell.

A public material heretic "Pope" cannot be Pope (because a Pope is prevented by the Holy Ghost from destroying the visibility and unity of the Church) but could go to Heaven if he embraces heresy through no fault of his own.  But one who claims ecclesiastical office, it would seem, does not have ignorance as an excuse.  All the V2 Popes until now have been born and raised in the true Church and were aware of what the Catholic Church has always taught.  Eventually, if God allows this to continue, we may have a "Pope" who really is ignorant of his heresy through no fault of his own, but if he teaches heresy, after being shown his error once or twice and pertinaciously holds to his heresy, he will not be a valid Pope according to Divine Law.  

The "Popes" since 1958 have be formal public apostate heretics of the worst kind imaginable.  These, should they die in this state, appear destined to Hell barring some last minute miraculous conversion.  

I wonder about how different things would be today if the shepherds would have done what they were supposed to have done as is stated below.

If the person who incurs the censure be the pope himself, since
there is no tribunal within the Church with the right to pass judgment
against him, he cannot be removed from his office, even though he be
under censure, and, according to the law, have no right to function as
the head of the Church. We, his subjects, are not permitted to do
anything about this. It is not within our right to declare his acts devoid
of validity, due to his having been expelled from his office. Yes, the
faithful may know well that he has committed a sin to which a censure
is affixed by the Church, but this knowledge in no way qualifies
them to declare him deprived of his office, or never to have been
elected. We should have to continue to obey him as the pope in all
those religious matters which fall within the ambit of his authority,
UNLESS he should command something which is sinful.

However, even though the hierarchy cannot take legal action
against an heretical pope, all of them together, or any one of them in
particular, can condemn his teaching; they can accuse him before
God's tribunal, warn him of his sins, and remind him of the divine
wrath. Should this measure fail to produce any correction, they can
denounce him before his subjects, the Catholic faithful, and warn
them that they are not to listen to his teaching. Indeed, not only may
the prelates of the Church do this, they have a most serious obligation
to do it, an obligation which is as grave as the heresies are pernicious
and scandalous. And if they fail to do this, they become a party to the
pope's crimes, and will most certainly share in his punishment.

Moreover, where the bishops default in their solemn duty to
protect the Church and God's Little Sheep, the priests and the
laypeople have not the right, but the duty, to raise their voices against
an heretical pontiff. They not only raise their voices to God in prayer
for the misguided man, but they also speak out to the bishops and the
priests, and among themselves so as to warn their brothers and sisters
in Christ that the plague of heresy has infected even their Holy Father,
and has rendered him dangerous and unclean.

Fr Wathen is wrong. He sets forth an illogical arrangement where a man no matter how apostate he was can remain head of the holy Catholic church. Why would a lay person who is in apostasy be out of the church but a pope apostate remain in the church? They are both equal before God, in fact, if one were to be expelled from the church earlier, it would be the pope apostate, because of the responsibilities incuмbent on him.

This is all my private opinion and my own reasoning, but I cannot accept the argument from Fr Wathen, which sets forward something ridiculous. The church is doomed if he is right.

No, you are basing your opinion on your knowledge of the popes' sins and your emotions, OTOH, Fr. Wathen is stating the law of the Church.

There really is no tribunal within the Church with the right to pass judgment against the pope - as you said in your OP. He cannot be removed from his office, even though he be under censure, and, according to the law, have no right to function as the head of the Church.

There really is, according to the law, nothing anyone can do about it.

IMO, there would be no crisis *IF* the shepherds did what they actually should have done, as Fr. Wathen said, instead of what they did.