The Pope is guaranteed by the Holy Spirit to be infallible only in matters of faith and morals. Else, the words of Our Lord would be open to any and every diabolical (mis)interpretation. For those who reject Jesus appointment of Peter as the head of His (Jesus’) Church, well, there is no infallible teaching. And nothing is certain. Which is why there are so many evangelical and protestant branches of Christianity.
So if i understand you correctly, you are saying that ensured perpetual magisterial infallibility is essential for assurance of what is of God, men and writings. And should I presume that being the historical instruments and stewards of Divine revelation (oral and written) means that such is that assuredly infallible magisterium. Thus any who knowingly dissent from the latter must be in rebellion to God.
Does this represent what you hold to or in what way does it differ?
Sure there is. God's word.