The Septuagint was not thrown out because it was "Christian." The Septuagint was thrown out by the rabbis (c. 90 AD) because it was in Greek and contained deuterocanonical books not found in the Masoretic Text (aka "Hebrew Bible"). The Christian books (the Gospels, the Epistles) that existed by the end of the first century were also thrown out.
The Christian canon consisted of the Septuagint and the New Testament, along with all deuterocanonical books of either Testament. The Protestant side rejected the Septuagint and the OT deuterocanonicals, in effect saying the Christian canon was wrong for 1,500 years; the OT books quoted and referenced by the Apostles, that is.
When I go to a bar and order a beer, the bartender will ask me for an ID because I am so handsome and youthful looking. As proof that I am of age I show him my driver's license and he accepts that as proof. So far, you haven't told us what you need to see
Well, you seem to know what proof is. That's is encouraging. :)
Next time you go to the bar, just tell the bartender that you are of age, to trust you and believe you are speaking the truth from your heart and see how far that will get you in convincing him.
If he refuses, tell him that he doesn't have the eyes to see that you are handsome and youthful and don't look old enough to drink, and see if that will change his mind.
If that fails, go one step further and tell him that only the "elect" bartenders have the eyes to discern your true age and that they don't need any proof, because they have the eyes.
When that fails, show him a computer generated statement that reads: "To whom it may concern: this young man is of age. I certify it. Signed: God."
When you are thrown out of the bar (assuming your youthful looks really make you a lot younger than you are), try using the other technique. It seems to work a lot better and you seem to know it quite well. :)
I thought I read earlier on this thread that there really is no official "canon" in Orthodoxy. And, I didn't think the Deuts were made OFFICIAL canon by any Church until Trent, in response to the Reformation. I think I have heard some Catholics say that it all really was official from 1100 years earlier, but if so, I've never heard what the purpose of the Trent canon (decree?) was, then.