I believe in a God who chooses, in individual election to glory without regard to merits and solely by the gratuitous selection of undeserving individuals by God,
Yes, and those who thus believe in Catholic and Thomistic Predestination know that God will bring those who desire to be Catholic but are not, and who strive to sincerely seek the Truth, to become Catholics and become subject to the Roman Pontiff before they die. We know this because dogma teaches it, and doctrine, and dogmatic facts, confirm it. If it is necessary for salvation to be subject to the Roman Pontiff, and if all receive sufficient grace to be saved, it follows that all receive sufficient grace to be subject to the Roman Pontiff.
but to posit that the elect will "get it right" on this question throws the free will of man,
A strawman. It is Catholic teaching that all men receive Sufficient Grace to be saved. And if Sufficient Grace leads a good-willed Muslim to Jesus Christ our Lord without affecting his free will, but empowering it efficaciously and supernaturally, that he may be saved, in like manner, it will lead a Sede-vacantist or an Old Catholic, who each deny several Popes or Councils, to be Catholic and be saved.
of men in good faith who are striving to know God through Christ and His established Church according to His revealed truths without denying a single one, into total irrelevance if a man can be damned for "getting the question" of the pope wrong in these damned, confused times of the Church's troubles.
There is no confusion in the Ordinary and Universal Magisterium. There is only confusion from ordinary laymen, who are confused and confusing others, for they do not understand that when the OUM testifies that the Pope is the Pope, that is the Church's infalllible declaration. This matter was not studied properly until relatively recently, but it has now become widely known; and the best we can do, just as we do to even Protestants and Orthodox, let alone non Christians, is first and foremost to believe that Truth, and secondly to preach it.
Pope Boniface: "we declare, we proclaim, we define that it is absolutely necessary for salvation that every human creature be subject to the Roman Pontiff.
Pope Pelagius: "I am greatly astonished at your separation from the rest of the Church and I cannot equably endure it ... Thus how can you believe that you are not separated from the communion of the whole world if you do not commemorate my name during the sacred mysteries, according to custom? For you see that the strength of the Apostolic See resides in me, despite my unworthiness, through episcopal succession at the present time"