You need to realize that many non-Catholic people will just raise the bar and say “I am not convinced…” regardless of what is offered just because it IS Catholic. Whenever I encounter someone like that, I break off talking to them because either A) they are not listening in good faith, or B) they are just not ready to hear, and the Holy Spirit is not finished with them yet. (As He apparently is with you. )
What came first, the New Testament, of the church? I mean, it HAD to be written by some human hands since we KNOW full well that God Himself didn’t pen a single inkdrop of it, right?
Where did those humans come from?
So…in order for there to have been a New Testament at all, the church had to write it didn’t they? They were not commissioned by Christ to do that, were they? No. They just did it. Good idea? Yes! Inspired by the Holy Spirit? Absolutely?
The New Testament itself tells us expressly what the pillar and ground of all Christian truth is doesn’t it now?
1st Timothy 3:15 But if I tarry long, that thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and ground of the truth. And this makes perfect sense since the Bible cannot interpret itself.
Your passage from 1st Cor. 4:6 carries this note in the New American Bible, and I confess that I missed it somehow but it does help a little to make sense of this passage. So then perhaps the Douay-Rheims Challoner has a better rendering with
"6 But these things, brethren, I have in a figure transferred to myself and to Apollo, for your sakes; that in us you may learn, that one be not puffed up against the other for another, above that which is written."
In reading that I have to suspect that St. Paul here is telling them not to “be puffed up” by reading into his & Apollo’s letters things that they are not saying. In other words…(sort of like certain non-Catholics do today.

), prooftexting with pretexts.
Also bear in mind that at the point that Paul wrote this the entire NT wasn’t even written yet and certainly wasn’t assembled and canonized the way we have it today. So he can’t be talking about the whole of the NT, now can he?
Moreover, this is now the 2nd time that you’ve brought this passage up as if it is really a problem for you to let go of Sola Scriptura, and I have to wonder what’s going on with that?
If your problem is with the Sacred Tradition of the faith and the considerations of the ECF in interpreting what scripture means, then you need to consider a couple of things.
- The ECF were much closer to the apostles and hence to Our Lord himself than we are or anyone else since their time.
- They were holy men and bishops of the early church, and guys like Ignatius of Antioch were discipled by St. John the apostle himself, so unless you are willing to believe that John failed to teach him correctly I’d say that his writings (to which you now have a good link, BTW) will offer us very good insights into the things that the church believed, thereby affirming the interpretations of the Word of God that we hold today.
Aside from this I am still unsure what it is that you mean by your posts. One verse and a sentence tells us pitiful little about what your real question is. If I’ve answered your concerns, cool. If not, then I beg you to be more specific.
Pax tecum,