I actually agree with you on OSAS, because it’s simply not Biblical, and agree to an extent that there is a correct interpretation to any given scripture, and it is not subjective; however, is it not your personal interpretation that the Catholic Church is the true church, or that the Magesterium is the interpretive authority? That’s circular reasoning. You’re accusing Protestants of a fallacy, but are also committing one yourself. The accusation of “personal interpretation” is often a straw man argument against non-Catholics. Most people don’t believe in personal interpetation, but correct interpretation. For the most part, the Bible means what it says, and says what it means. The only time it doesn’t do this is when it makes use of Jewish idioms and makes statements in a cultural context. There is no need for a Magesterium to interpret, just a little homework.
The vast majority of differences from Catholics and Protestants come from the assumptions that each brings to Biblical interpretation. For Catholics, it’s deference to the Magesterium. For Protestants, it’s deference to the philosophies of either Calvin or Luther, (sola scriptura, sola fide). Simply making an observation here, not agreeing or disagreeing with any of these.