You are trying hard and doing some good research.
But you are overlooking the elephant in the room.
And the elephant is this: St. Thomas Aquinas did not live during the time of the great apostacy. Nor was he writing in regards to how the consequence of his reasoning would be different under such a scourge.
It makes a big difference when you look at the elephant and admit it's an elephant.
You can't just assert this. How does this change matters? Jurisdiction has to come through the Church, according to ecclesiastical law, or at least the tacit consent of the Roman Pontiff. There's no other way, according to the Divine constitution established by Christ, Tu es Petrus et super hanc petram aedificabo Ecclesiam meam ... Tibi dabo claves regni caelorum. As the Abbe de Nantes says, commenting on Msgr. Lefebvre's assertion of jurisdiction (For the Church, Vol. 3, Chapter 9):
How pitiful! "Such a demonstration is, alas, quite worthless", the Abbé de Nantes will write." And the theologian of the Catholic Counter-Reformation will prove this easily. Let us read what he says: "The Code of Canon Law recognises objective extraordinary circumstances, that is to say, circumstances which are specified by law, incontestable, and necessarily recognised by episcopal and Roman authority. The Code provides for these circumstances precisely in order to prohibit any subjective interpretation and to put a stop to private judgements all too eager to find ways of avoiding ordinary episcopal jurisdiction."Thus, it is recognised that any priest, even an irregular one, has the right to confer the sacraments of salvation on a person who is in positive and proximate danger of death. But in order for a priest to organise a regular Catholic ministry outside the knowledge and power of the local Ordinary, three conditions are necessary: 1) that he himself be a bishop, 2) that the local hierarchy has been destroyed, annihilated or impeded, and 3) that the moral consent of the Sovereign Pontiff is positively certain (cf. Dom Gréa, L’Église et sa divine constitution, p. 235-238).
"Mgr Lefebvre personally fulfils the first of these conditions. Not the others. To say that the second is realised, is to judge without appeal – and I employ the term in its strict juridical acceptation – that nowadays there is no longer any episcopal Body on earth, or at the very least that there is no longer any bishop in this country… As for the third condition, to maintain this, one would have to make out that the Pope is drugged, that he has a double, that he is confined to his room, or else roundly state that there is no longer a true Pope…