The canons don’t "presuppose" anything in terms of jurisdiction; they even tend towards redundancy at times. They were the disciplinary rules of the Church. Even St Maximus notes this in your quote, but you haven’t provided a single canon defending this "Divine right"..

You ask if I agree with St Maximus.

Earlier you provide a fuller quote: "for he speaks in vain if he thinks he is persuading people like me, if he does not satisfy and implore the blessed pope of the most holy city of Rome, that is, the Apostolic See". [PG 91: 144]

St Maximus had a lot of explaining to do to his brethren in the Christian East, considering he thought the most (if not all) of the Eastern Church to be in heresy. Does he state that the Bishop of Rome has a primacy of Divine Right? No, but "keys of orthodox Faith and Confession…closes every heretical mouth". From an Orthodox standpoint, this is acceptable. It goes without saying that heretics who usurp the Roman Patriarchate do not hold the keys because of the "Chair", but only insofar as they hold the Orthodox Faith. The gates of hell could not prevail over Rome, who represented all of Orthodoxy, because her Bishops were Orthodox.

I have also pointed out that St Maximus demonstrated a willingness to break communion with every Bishop, if necessary, to preserve his Orthodoxy. So even without the entire text, I can’t really see why I would say no, since he doesn’t seem to help your argument at all, but focuses on Orthodox Confession. My answer is yes. I agree with St Maximus.

Question #2:

Since almost every argument you adduce includes "the Apostolic See" in your texts, I’d like to bring this to your attention again:

Your most sweet Holiness has spoken much in your letter to me about the chair of Saint Peter, Prince of the apostles, saying that he himself now sits on it in the persons of his successors. And indeed I acknowledge myself to be unworthy, not only in the dignity of such as preside, but even in the number of such as stand. But I gladly accepted all that has been said, in that he has spoken to me about Peter's chair who occupies Peter's chair. …And to him it is said by the voice of the Truth, To thee I will give the keys of the kingdom of heaven (Matth. xvi. 19). And again it is said to him, And when thou art converted, strengthen thy brethren (xxii. 32). And once more, Simon, son of Jonas, lovest thou Me? Feed my sheep (Joh. xxi. 17). Wherefore though there are many apostles, yet with regard to the principality itself the See of the Prince of the apostles alone has grown strong in authority, which in three places is the See of one. (To Evlogios, Patriarch of Alexandria, Ep XL)

Do you agree with the above statement of Pope St Gregory the Great? If not, why?