Three questions for you: how many books are canonical, on what basis is a book deemed canonical, when were they canonized?
Tell that to Jerome who translated the Latin Vulgate.
The Dead Sea Scrolls are the biggest vindication of the Masoretic Text. It shocked scholars around the world that the text of the Old Testament remained uncorrupted over so long. There are more than just the apocrypha contained, you wouldn't consider the Bar Kokhba Letters canonical, would you?
I trust that the Eastern Orthodox Church had nothing to do with how Protestants got their Bible.
This is a good response from your perspective, my response would be:
1. The whole Orthodox communion accept 76 books as canonical. This doesn't mean that there aren't other writings that are sacred. But whatever has been accepted as sacred scripture is sacred scripture and will never not be sacred scripture. The basis for deeming something scripture is its origin, (the local churches attest to the origin of their local letters) its use within the liturgical life, and The Apostolic preaching, the trustworthy tradition handed down to us. That helps us determine what is forgery, and what is not. For the deuterocanonicals, these are texts which were translated by monks into languages of new Christian peoples, because they were written by Hebrew scribes or even prophets (epistle of Jeremiah,) and were accepted by the Early Christian community, because that is where Christianity originated from. The Sadducees didn't accept any canon after the books of Moses. The same question can be applied to the question of why we accept the Psalms, Prophets, Wisdom, or Chronicles sections of the Bible. We accept them, because
One: The majority faithful living community of the people of God accepted them and God worked with the prophets. & Two: The teaching and truths within these scriptures are in continuation with the exile and redemption through Moses and with his writings.
Did God reveal new things after the books of Moses? Yes. God promised He would be with his people and reveal further His plans, even if it comes from a lowly pious faithful scribe such as Ben Sirach, or through the history of martyrs and fighters like in Maccabees.
2. St. Jerome used manuscripts, but he did it within the context of The Church, and accepted manuscripts to be translated within the criteria that I mentioned in my 1st response. He was also not an archeologist, he was Orthodox and made sure that he did not write down heretical typos, and any
non-heretical discrepancies can be improved upon by later scribes. The criteria for scripture is that it is sacred and teaches what Christ desires to be taught.
3. Thank you for sharing that. Genuinely, I will look more into that. I will take it with a grain of salt just like I do the books of Enoch especially 2nd and 3rd, as the dead sea scroll community were not in full unity with The Jerusalem community. But I have no doubts that the second temple Jewish people accepted in general what we call deuterocanonical. There are writings that aren't apocryphal that you accept that aren't required to be written by the highest form of prophet, David is also a prophet, but not in the same way that St. Isaiah is. There are also writings within that period that are lost, or were very much localized, that don't necessarily mean they weren't used for a sacred purpose by God for those specific readers, and writings that were used for edification but not held on the same level as liturgical scripture, such as Enoch which have objective truths within them. The pharisees accepted apocrypha as well, and it was only until after rejecting Jesus that they cut their readings. Christ mentioned the seat of Moses and gave authority to it in the same way that he says hearken to what the pharisees and priests (not the saducees or samaritans who were heretics) say, but not to what they do. The seat of Moses is not mentioned in any of the Old Testament, apocrypha included. That's because tradition that is pleasing to God is the basis for what is sacred.
I will personally ask someone more knowledgeable about the content of the Bar Kokhba Letters, first my priest and anyone else, and I recommend if you are able to contact him ask Fr. Deacon Ananias or someone who specialize in The Biblical Canon.
4. I respectfully disagree for the prior and above mentioned reasons, because The Church and Saints are why scripture has been preserved in its translated form and why I can trust that 76 books of our canon are God pleasing, sacred, and edifying to be read within the context of The Church.
As a note, holy tradition is equal to scripture, and it is why scripture exists. It has its basis in revelation and in Christ's incarnation, because The Apostles wanted write down the basis of their preaching, and the Prophets wanted to write down God's word on His present and future actions. The Gospels are written with help of eyewitness who preserved the sacred oral truth, does not contain everything that could possibly be written as the ending of John indicates, and the epistles are written to Churches that had already received baptism, laying on of hands, sacred oral teaching of The Apostles, and received communion weekly which is blessed alongside the prayers of the presbyters. They doubtless heard of Mary, and of the miracle of the virgin birth as well. They doubtless read the didache as it was sent throughout the churches. Scripture and tradition both exist within a relationship that is lived as a life. It was the same for The Hebrew people that God had called, therefore it is the as it was then and now today.