The pope was legitimate when he convened the Council, you cannot even think otherwise much less prove it. - Stubborn
Ecuмenical Councils are those to which the bishops, and others entitled to vote, are convoked from the whole world (oikoumene) under the presidency of the pope or his legates, and the decrees of which, having received papal confirmation, bind all Christians. - Ladislaus
This is exactly why I said if you believe what you posted here from the CE, which agrees with all that you claim as regards the magisterium, then you cannot revert by saying the pope was illegitimate since to do so is to reject "the sure teaching of the Church" (the CE quote), in order to maintain your own, unproven opinion shared by few.
A council, Ecuмenical in its convocation, may fail to secure the approbation of the whole Church or of the pope, and thus not rank in authority with Ecuмenical councils. Such was the case with the Robber Synod of 449 (Latrocinium Ephesinum), the Synod of Pisa in 1409, and in part with the Councils of Constance and Basle.
The popes were true popes. This is the proof you are up against. The conciliar popes were all elected by the college of cardinals, same as always, they accepted their election and according to the law of the Church, were instantly the true pope, same as always - this election and acceptance is the infallible sign of legitimacy, same as always, it is the way the whole world knows who the successor of St. Peter is now and forever - same as always.
If in fact it turns out that V2 was a Robber Council, a future pope will be the one to make that decision, no one else - same as always. Until then, history proves that V2 was a genuine Council of the Church complete with pope and all the bishops of the world under him, by your own definition V2 was a genuine council of the Church and from it came forth the NO errors which are so bad, that to submit and join the NO is a sin.