Even if the ridiculous notion of a pre-Christian LXX was valid, it would be in violation of Scripture(KJB):
1) The sole custodians of the Old Testament Scripture was the Levites, according to Deuteronomy 17:18; 31:25-26,and Malachi 2:7.
Not exactly so, following is a rebuttal to the Scriptures you have cited but not quoted and an important oversight on your part concerning this matter.
Deuteronomy 17:18
And it shall be, when he sitteth upon the throne of his kingdom, that he shall write him a copy of this law in a book out of [that which is] before the priests the Levites
In the CONTEXT, this is a duty of the King of Israel and has NOTHING to do with the TRANSLATION of the Word of God for public dissemination.
Deuteronomy 31:25-26
That Moses commanded the Levites, which bare the ark of the covenant of the LORD, saying, Take this book of the law, and put it in the side of the ark of the covenant of the LORD your God, that it may be there for a witness against thee.
Ibid reason above, this is a singular witness against the Hebrews and has nothing to do with the LXX translational issue.
Malachi 2:7
For the priest's lips should keep knowledge, and they should seek the law at his mouth: for he [is] the messenger of the LORD of hosts
Again, this is a bogus claim that the Levites were ALONE keepers of the Word of God from the very verses you have given, the kings of Israel/Judah were not Levites and they were to make a copy of the Law, David was of Judah and God used him to WRITE some of the Scriptures, the prophets were not Levites and they also wrote and kept the Scriptures. AGAIN, there is nothing about a translation of God's Word in this passage.
The LXX was a translation of the Word of God and not a copy of the original Hebrew language text.
I am not able to find one rule concerning the translation of the Hebrew into another language in the Law. If you know of one which specifically speaks of translating the Hebrew Word of God into another language and requires a Levite to do the same please let me know where it is found.
2) God ordered his name NOT to Be spoken of in the land of Egypt by the Jews, Jeremiah 44:26.
Jeremiah 44:26
Therefore hear ye the word of the LORD, all Judah that dwell in the land of Egypt; Behold, I have sworn by my great name, saith the LORD, that my name shall no more be named in the mouth of any man of Judah in all the land of Egypt, saying, The Lord GOD liveth
Again another unreasonable claim for more than one reason; first of all the Jews didn’t say the name of God in or out of Egypt which proves that the Scripture could and was copied without the necessity of saying the name of God, they were silent when it cam to the name of God or simply said HaShem indicating that the name of God was present in the text. This reason Is sufficient to show that your logic is wrong. And just to be consistent we are talking about a translation above and beyond the speaking of the tetragrammaton.
I could have and may yet expand the context from which these citations were isolated.
The bottom line is that the LXX was a translation and not defined as a duty of the Levites neither are there rules concerning the translation of either the Old or New Testaments as “translations”.
HankD