Vatican II is not the Church.
You quote Lefebvre and so many times I hear quotes of his or the SSPX here but he explicitly condemned the position of sedevacantism.
"Now these recent acts of the Pope and bishops, with Protestants, animists and Jews, are they not an active participation in non-Catholic worship as explained by Canon Naz on Canon 1258-1? In which case, I cannot see how it is possible to say that the Pope is not suspect of heresy, and if he continues, he is a heretic, a public heretic. That is the teaching of the Church.
Now I don't know if the time has come to say that the Pope is a heretic; I don't know if it is the time to say that. You know, for some time many people, the sedevacantists, have been saying "there is no more Pope," but I think that for me it was not yet the time to say that, because it was not sure, it was not evident, it was very difficult to say that the Pope is a heretic, the Pope is apostate. But I recognize that slowly, very slowly, by the deeds and acts of the Pope himself we begin to be very anxious.
I am not inventing this situation; I do not want it. I would gladly give my life to bring it to an end, but this is the situation we face, unfolding before our eyes like a film in the cinema. I don't think it has ever happened in the history of the Church, the man seated in the chair of Peter partaking in the worship of false gods.
What conclusion must we draw in a few months if we are confronted by these repeated acts of partaking in false worship? I don't know. I wonder. But I think the Pope can do nothing worse than call together a meeting of all religions, when we know there is only one true religion and all other religions belong to the devil. So perhaps after this famous meeting of Assisi, perhaps we must say that the Pope is a heretic, is apostate. Now I don't wish yet to say it formally and solemnly, but it seems at first sight that it is impossible for a Pope to be publicly and formally heretical. Our Lord has promised to be with him, to keep his faith, to keep him in the Faith - how can he at the same time be a public heretic and virtually apostatise? So it is possible we may be obliged to believe this pope is not pope."
-- Archbishop Marcel Lefebvre, "Address to Seminarians," 30 March and 18 April 1986.