I see it sort of like the right to bear arms: a gun in every citizen's hand protects a strong republic the laws by which we can all agree on, a bible in every believer's hand protects a strong church, we can read it ourselves, we don't need the state or the government or whoever, telling us what it says.
3, I'm sorry but the rest of your post is unintelligible
It is true that the Eunuch was not baptised, but Acts 8:31 nevertheless says that he needed help understanding the scripture, and verse 35 says that St. Philip preached -- that is, interpreted, since the book was on the Eunuch's lap, -- the scripture. Thus understanding comes from apostolic authority, not from just the text. And we observe thie same thing today, -- baptised and even confirmed Christians hold opposite views on the scripture, so some of them had to interpret it wrongly.
We do not believe in private interpretations of scripture
Thnak you for saying that. Who are "we"? Most Protestants on this thread would say that they feel comfortalbe interpreting the scripture for themselves. My opinion is that they are mistaken, and they take Luther's or Calvin's or Don Brown's interpretation, but pretend it is their own.
unintelligible
I gave several examples of who one needs to know Greek and the Middle-eastern culture of antiquity to understand translated scripture. The point is that although theology is culture-invariant, we don't get the theology directly from the scripture as very little of it is in the form of theological treatise. In order to get theology form the scripture, one has to first understand the scripture, like the Eunuch in Acts 8, and for that apostolic authority is necessary, or else you get da Vinci code nonsense out of your scripture-reading.