4) And how do we know what an ecuмenical council is? Usually the presumption is just "if the Church says it is, it is". And then if the Church tells us it's ecuмenical, we can be sure its teachings are true. But with this universality argument, now the Church telling us it's ecuмenical isn't good enough, and we must judge for ourselves(with our fallible judgements) whether or not the council possesses universality. So we have no way of knowing for sure which councils are ecuмenical or not.

Meanwhile, you would defend the authenticity of a council which is lacking in infallibility and universality (and is clearly therefore no dogmatic fact, yet persist in this defense even though we know ecuмenical councils must be dogmatic facts), and pretend to find no distinctions between Vatican I and Vatican II, so as to create irony.

I don’t see that at all.

Why wouldn’t you know if novelty is taught, thereby robbing a council of universality (and therefore of legitimacy)?

You yourself know novelty was taught at V2, and therefore you reject it.  So it seems you are creating an argument which you yourself don’t believe.

I have [...] appealed to the notion of the overall indefectibility of the Church.

Pastor aeternus [...] ita in Ecclesia sua pastores et doctores usque ad consummationem saeculi [Mt 28,20] esse voluit.

Dei Filius et generis humani Redemptor Dominus Noster Iesus Christus, ad Patrem caelestem rediturus, cuм Ecclesia sua in terris militante, omnibus diebus usque ad consummationem saeculi [Mt 28,20] futurum se esse promisit.

CHAPTER XXVI. Concerning the Antichrist.

It should be known that the Antichrist is bound to come. Every one, therefore, who confesses not that the Son of God came in the flesh and is perfect God and became perfect man, after being God, is Antichrist. But in a peculiar and special sense he who comes at the consummation of the age is called Antichrist.

All I know is that Vatican II taught error.

But drew believes that the proximate rule of faith is the set of dogmatic doctrines of the Church.  This is why he believes Bergoglio is the true pope and also why he believes he can justly resist the pope and use his own private judgment to overrule the pope’s decisions.
The Church on the other hand teaches that obedience to the pope is necessary for salvation.  But it was always necessary to use our own private judgment to identify the pope and the true hierarchy of the Church. E.g. St Vincent Ferrar vs St Catherine of Siena during the Great Western Schism.
So if you believe that it is the pope who is the proximate rule of faith, then in order to know what the Church teaches, you first have to identify who is the pope or in the case of an interregnum, who are the legitimate hierarchy of the Church.
In the case of V2, no one disobeyed the supposed pope in 1965.  It wasn’t until at least 1967 that anyone questioned the legitimacy of the pope (Shuckhardt).  The traditional Catholic movement didn’t start until 1970 at the earliest after the new “Mass” had already been concocted.  So it wasn’t a problem with the texts of V2 (although the problems certainly were there) that sparked the traditional Catholic movement, it was the founding of a new religion with the Mass being the most obvious manifestation.
It was only after the fact of the new religion that we traced the problem back to V2.  And for sedes, it was traced back to the elections of 1958 and 1963.
If Vigano is going to have any success at uniting the clans he will have to address the new religion and its positively doubtful sacraments.  I wonder if he will have the courage to do that since his own legitimacy will come into question.