That's fine. The Jewish faith can determine whatever books they choose to have in their Scriptures.
Again, this is fine, but it was the Old Testament used by the early Christians. (And again, the Scriptures used by Greek speaking Jews in diaspora)
Yet the Greek Septuagint is the text used by New Testament authors.
I realize this. This argument however sounds very Roman Catholic. Aramaic was the common language spoken so Matthew 16:18 reads, "And I tell you, you are Peter (Kepha, Aramaic for rock) and on this rock (Kepha) I will build my church . . . "
And St Jerome's Vulgate (late 4th century) includes some of the "Deuterocanonical" texts: the additions of the Song of the Three Children, the Story of Susanna and the Story of Bel the Dragon to the Book of Daniel. His Psalms come from the Septuagint, the additions to Esther, 1 and 2 Maccabees, Wisdom and Sirach.
That's fine. There are other Old Testament Books which are not quoted in the New Testament.
Bingo, hence, the Scriptures the Greek speaking Christians used.
And some scholars agree that Matthew Gospel was actually written in Aramaic.
But it was the language used by most Christians and the Septuagint was the text they used. It was not until the early to mid 2nd century that the Jews put together an "official" canon. The Jews at the time of Christ did not have an "official" canon. Greek speaking Jews used the Septuagint and the Sadducees used only the Books of Moses. St Paul writes, speaking of the Old Testament, that "all Scripture" is inspired. Well, the Septuagint has "all" the Old Testament text since St Paul wrote his Epistles in Greek, his quotes of the Old Testament in his letters come from the Septuagint. There are plenty of studies, and not only from Orthodox sources mind you, that show this.