But these are written, that you may believe that Jesus is the Christ, the Son of God: and that believing, you may have life in his name.
-- John 20:30-31
The Gospels exist to lead man to Salvation through Christ. Everything else is extraneous; however, that doesn't mean it didn't happen, it simply means that knowledge of it wasn't deemed necessary for OUR Salvation.
The inherent fallacy of sola scriptura (at least to my way of thinking) is the notion that if something isn't mentioned in the Bible, then it isn't true. Yes, everything in scripture is true, but that doesn't mean that everything not in there is false.
I can't know your heart, but you really should think about what we mean when we say Sola Scriptura. The belief is often misstated for the purpose of ridicule. The best example of it is the Bereans and the high esteem they were held in because they adherred to it.
Sola Scriptura does NOT teach that something must be found in the Bible to be true or "good". Rather, it teaches that the sole earthly authority for Christians is the Bible. Therefore, if it is in the Bible, then it is true. If it is not in the Bible, then it might be true or not true. If it contradicts the Bible, then it is definitely NOT true. I fully grant that interpretation of the Bible plays a huge role in how this doctrine is implemented, but my view is that is not the doctrine's fault.
For example, you make the sign of the cross on your chest. This is nowhere in the Bible. However, it also does not contradict the Bible, so it does not violate Sola Scriptura. The same can be said about my altar call. Problems arise in such cases as the Marian doctrines, in which case we assert that there is a direct contradiction in scripture. That is the deal killer, NOT that it is simply an Apostolic belief. I think that if many Apostolics could parse the doctrine down to its barest bones, that many could find "some" sympathy with it.
Clearly, since the doctrine was promulgated by Reformers certain assumptions are made. However, my personal view is that the interpretive assumptions are not proving as to the validity of the doctrine itself. IOW, I would much rather hear an Apostolic say: "All of my truly core beliefs via Apostolic interpretation are found in the Bible, and here's where they are ..." (Sola Scriptura). This is as opposed to: "Many of my core beliefs are found in the Bible, and some other core beliefs are found in extra-scriptural Tradition, and here's where they are...".