While I agree that a personal knowledge of the Scriptures is valuable, I don’t know if what you’re trying to say is actually supported by the texts you quote. Many people in the 1st century weren’t even literate. Additionally, they didn’t have personal copies of the Bible, or of Torah scrolls in their houses to study. This means that study was done in community settings, led by…a teacher or teachers.
It means the Bereans likely studied out Paul’s message to them under the guidance of more qualified teachers, although that certainly doesn’t discount each person’s personal involvement in such study. It means that prophecy not being of private interpretation had more to do with it being in agreement with the apostles’ teaching and not of lone teachers hawking their private understanding. What individuals had access to was not so much their own understanding through personal bible study, but the commonly held teaching by the believing community, of the apostles of Jesus. And, Paul’s counsel to Timothy to study to show himself approved, was council to a person functioning in a pastoral/teaching role in the church in Ephesus, not to every member of the church there.
This leads to the second complexity of you’re position. You say that we need to let one Bible text interpret another. Do you mean proof-texting? If so, this is notoriously unreliable in that it lacks any controls of literary context, cultural and historical backgrounds, life settings, etc. of the original text. In the quest to let the Bible interpret itself, all of this is often ignored. The text is flattened out into a two-dimensional monochrome in the quest to harmonize everything one thinks the bible is saying on a topic, and what often comes out is a distortion of meaning rather than what the texts are actually saying in their original settings.
This is the methodology of popular, protestant biblicism, and what it often produces. It also has helped lead to thousands of different denominations and doctrinal positions, all claiming to result from the bible interpreting itself. Adventism sits in the midst of this interpretive tradition. It is fraught with its own set of problems.
All this leads to the idea that theologians, teachers, those with knowledge of biblical languages, cultures, etc., are gifted people that God has set within the Christian church. But, even beyond this, knowledge of the Bible, as you said, is not the goal. Knowing God through Jesus is. Being equipped to live out our faith in love, in community, and in faithful service to each other and others is. This is so much more the stuff of knowing God, than having every doctrinal duck lined up in a row.
As Jesus said to those who knew the Scriptures backwards and forwards, “You search the Scriptures, for in them you think you have eternal life. But, they are they which testify of me…” And, the Jesus to whom the Scriptures testify, was about self giving love, and faithfulness above all other things.