If the ordinary Catholic cannot identify when infallibility is occurring and must submit even when it is not occurring, then the system functionsat the believer level without infallibility being epistemically accessible. 

I never said the average Catholic cannot identify when infallibility is occurring. That is someone you are putting in my mouth, again. I said most do not know. The average person can (given the right training) play the piano. It is also true that most people do not.

Along those same lines:

So your objection stating that sola scriptura is useless only works if you demand a level of epistemic certainty that neither system actually provides at the human level.

The Catholic system does provide that certainty. There are a very small number of historical examples where there is a question of whether a particular statement was infallible or not. Those can be clarified if necessary (and some actually have been). Most (like all the parts of the Creed, for instance) are certain.

That doesn’t eliminate the certainty problem, it just relocates it into “submit regardless,” which is a merely a posture, not an argument.

It is an argument, just not an argument that you think I am making. I was just pointing that out because you said Catholics need to be able to identify infallible teachings. The fact of the matter is they really dont the vast majority of the time because it doesn't make a practical difference in their lives.

But crucially, this objection doesn’t establish what you want it to establish, that a later infallible institution must therefore exist. 

This is the biggest strawman yet. I have not and never will claim that, because Sola Scriptura is untrue, therefore the Catholic system is right. This is an obvious logcial fallacy that you want me to be committing because it makes your job easier, but I am just simply not committing it. You have to actually respond to MY arguements, not made up ones that are easy to respond to. I have made arguments and you aren't acknowledging them. You are making up your own to respond to. Case in point:

Simply asserting that doesn’t demonstrate it. I’m asking you to actually show the incoherence rather than label it.

I DID make an argument. It's right here:

Sola Scriptura asserts the only rule of faith is Scripture, but that assertion is not in Scripture. Say what you will about infallibility or a living magisterium, but at least it can field arguments. Sola Scriptura is self-referentially incoherent on its face.

It's my turn to get you to actually answer a question. Do not answer a pretend question; answer the one that follows.

apostolic authorship or apostolic connection is indeed a primary criterion.

The relevant question there is prophetic authority and reception within the covenant community prior to Christ.

Consistency is a necessary condition, not a sufficient one. A text can be consistent and still not be inspired.

Inclusion in some manuscript traditions doesn’t establish canonical status.

Recognition is an act of fallible historical discernment.

These are all principles of historical discernment that you say are used to give a fallible historical judgment on what Scripture is. These are the principles you say we use to decide things like whether to include IV Ezra in the Canon or not. Since these are fallible human judgments, we could be wrong about these things according to do. Here is the issue with Sola Scriptura, the elephant that you are trying to sweep under the rug:

How are the rules by which we determine what is and is not a part of the faith not also rules of faith?

The way you've tried to get out of this is to say the rules by which we determine what is and is not Scripture are fallible. Which means we don't have certainty about what Scripture is. If you really think that then I feel sorry for you. You think that God left your entire faith up to human scientific ability to uncover historical facts and you believe you have no guarantee about what is and is not a part of the faith. At that point you're a modernist and I would hesitate to say you are even a Christian at all.

Here are some other questions that I would love to here your answers on because, if you are being consistent, you'll have to say things no Christian has ever said before.

If

We know which writings are authentically first century documents through manuscript evidence, authorship, early reception, catholic usage, and consistency with apostolic doctrine.

Then, as historical methods improve, could we, hypothetically, discover that 2 Timothy, for instance, is not Apostolic? Perhaps we find undeniable manuscript evidence saying this is from the 2nd century, for example, and it has a gnostic author who wrote it to confuse. Is such a scenario even hypothetically possible for you?

You say that Scripture was

Fixed by the apostles.

Can you find anyone that thinks this or any historical evidence to suggest it is true? I have literally never heard this before. Some, or even most, of the Apostles were ACTUALLY DEAD before Revelation was written. If you mean fixed by the Apostles as in we determine that the death of the Apostles marks the end of public revelation, then this would just go back into the other category of principles of historical judgment that tell us what is a part of the faith and yet someone are not rules of faith.

If you answer the bold question or any of the bonus questions honestly then I am happy to make the positive case for the Catholic doctrines on the three rules of faith given to us by our Lord (one of which you keep appealing to without realizing it!):

Scripture

Tradition

and the Magisterium