Um, not to put a damper on your enthusiasm, but you might want to checkout the history of the Council of Carthage and the deuterocanonicals. Your research on Luther is far more in-depth than anything I've ever known or attempted, but it is my understanding that Luther removed the Deuterocanonicals (the Old Testament ones for sure) due to the arguments when the Canon was closed. The Old Testament books are: 1&2 Maccabbees, Wisdom, Sirach (or Ecclesiasticus), Tobit, Judith and Baruch along with parts of Daniel and Ruth. The New Testament ones are, yes, Hebrews, James, 1&2 Peter, Revelation and one of the epistles of John. This is what Sts. Augustine and Jerome got into a big argument over and what the bishop of Rome at the time settled when the statement "Rome has spoken" was made.
In the Old Testament case, Jerome was living in Jerusalem at the time and was very much influenced by the Jews there. The seven deuterocanonicals are not from the Hebrew canon, but from the Helenistic tradition of Judaism. Sort of interesting when there are more parallel quotes of Christ from Sirach than almost any other NT book. Essentially, Augustine won the argument.
I don't remember the details as well on the NT books. But they were called into question and I know Revelation was one of the last ones approved.
That's one Council that's worth studying. St. Augustine's intellect is so very much on display.
Not sure what your source is, but it’s deeply mistaken. St. Jerome commented that he could not prepare a translation of the Deuterocanonicals because he did not have an original Hebrew text, and this, in his bible published as a translation from the Hebrew, he only included them in an appendix of sorts. His enemies used that action as an excuse to oppose him, alleging that he denied the authenticity of scripture. He responded by explaining his actions, and stated that anyone who insisted he had denigrated the canonical status of the Deuterocanonicals, “a fool and a slanderer.”
Martin Luther rejected 14 books, not just 7, for the reasons I stated. He was unable to convince other Protestant groups (Calvin, Henry, etc.) to disregard the New Testament deuterocanonicals, but presented Jerome’s comments (yet not his explanation) as a basis for rejecting the OT deuterocanonicals, plus the reason you cite. Since the Jews did not receive the NT at all, that explanation also couldn’t cover the NT. We now understand that the Jews adopted a canon rejecting the deuterocanonical OT books but including all other OT books only after Christ, in direct opposition Christ.