You as a bible researchers, refused the [sic] catholicism, but still use the books which catholic church defined as the source of truth.
I'm Jewish. We've been using the Bible long before there was a Catholic Church or Gentiles came into the picture, but...
You may be confusing the Roman Catholic Church with Marcion of Sinope and his followers, the Marcionists. Jehovah's Witnesses have often been compared to Marcionists as have been several other of the NRMs that have come forth from the Second Great Awakening, notably the sister religion of the Watchtower religion, the Worldwide Church of God (now defunct).
Roman Catholicism does not hold that Scripture is "the source of truth." In fact, it teaches (and always has) that Jesus Christ is "the source of truth." (CCC 2466) This was actually the reason for the controversy between Marcion of Sinope, his rejected canon, and the eventual canon of scriptures devised by the Catholic Church which would come to be called "the New Testament."
Marcion was a bishop of the 2nd century C.E. whose father actually purchased his bishopric rights for him. It appears that Marcion though highly educated was far removed from the people he was supposed to serve, and due to his upbringing was focused upon making a name for himself in history. And that he did, altough it would become one of great infamy.
Having a great love for the Hellenists, Marcion was obsessed with Greek mythology and religion. He began to see in the teachings of the Gnostics comparisons of "the select" who were granted special salvific divine status as possibly applicable to Jesus Christ. He devised a way to combine the two by rejecting everything that was not "Greek" about the Gospel, and creating a formula in which people could "learn" their way to salvific divine status, to become a "god" like Jesus.
This entailed rejection of all that was Hebrew about the religion of Christianity, including the rejection of the Septuagint. Since by the 2nd century, Christians were already considering that Jesus was likely divine, Marcion began to teach the Jesus was simply one of the gnostic-like "demi-gods" of the select who reached this status via gnosis or special divine knowledge. This knowledge, however, was in the reach of some others if they applied themselves.
Taking the writings of the apostle Paul, editing them for any mention of the Jews that favored them (this meant rejecting his letter to the Romans), and finding a gospel that was written by a gentile convert in Greek that he would claim was his own (that he edited as well), Marcion devised what he called was the "rule" (or in Greek kanon) for salvation. Anyone who studied it could expose themselves to the proper knowledge that led them to become like the demi-god, Jesus.
Marcion gained followers and felt his place in history and the Church was now solidified. He felt all he had to do now was go to Rome to show the Pope what he had done. But upon arrival it is reported that Marcion was "surprised" when he found himself excommunicated for his efforts.
Apparently he had been warned along the way to stop his work but would not listen. Gnosticism had been the Church's greatest threat. And while the Church treasured the Scriptures, it never viewed salvation as based upon one's study of them. Some people could not read as many people in the world were still illiterate in those days. Salvation, the Church taught, was katholicos or universal (where we get the word "Catholic" from today). Any person can be saved whether they read the gospel for themselves from the Bible, hear it preached from a sermon or learn it from another Christian who teaches it to them personally. One isn't saved via contact with the Scriptures, no matter how holy these texts are. People are saved, the Church teaches, via Jesus.
To stop the Marcionist threat, the Church studied the spreading problem as copies of Marcion's canon were growing. It appeared that Marcion had merely copied the gospel of Luke and claimed it as his own, minus the first two chapters (because they are very "Jewish"). And spending about almost 200 years of study and discussion with the churches around the world regarding what was being used during the liturgy, the New Testament was eventually (albeit slowly) canonized. It was not the basis for the faith, but the standard for what was Scripture for the Christians to counter the Marcionist movement.
If you notice, it is heavy with Pauline writings and includes a non-apostolic gospel, that of Luke. This is due to Marcion since his Bible used only the works of Paul and stole that singular gospel. Marcion claimed Paul was anti-Jewish. So the Church proved that he was not by using Paul's best work, especially Romans to counter Marcion. Romans even begins the Pauline library if you notice, and in it Paul teaches that despite the fact that the Jews rejected Christ, the covenant is still intact and that somehow, in the end, the Jews will still be saved.
Luke, even though not one of the apostles, is a witness to Jesus as a gospel writer. He even writes the only history of the apostles in the canon. This is likely to counter the claims of Marcion. Luke is likely a Gentile convert to Judaism. Marcion claimed he wrote the gospel of Luke and that Judaism was rejected by Jesus and unnecessary. But if you replace in the portions of this gospel that Marcion removed (chapters 1 & 2), they are some of the most Old Testament-sounding pieces found in the whole New Testament. Mary and others sing in canticle form to the Lord in Hebrew style and the Temple is described in detail. In both Luke and in Acts it is demonstrated that Luke and Paul obviously worshipped in the Temple regularly, a point Marcion would not have other know.
Except for groups like the Jehovah's Witnesses and a few other rare Fundamentalists that may be labeled as cults as well, most Christians, even Sola Scripturians, do not rely solely on Scripture alone. Much Tradition lies at the center of their faith. The creation of the canon, for instance, is Tradition, and belief in it as a Standard is outside of the Bible's scriptural reach as there are no Bible texts that tell us what books should be in the Bible and what should be excluded, or that there should even be a divine library in the first place.
But one thing is clear: Catholics do not teach that the Bible is the source of salvation. If they did, the Protestant Reformation never would have occurred.