The MT is not a translation. And even though the LXX is a translation, it comes from a Hebrew text that agrees with it. So it shouldn't be considered a translation either.
That depends on your beliefs and what you find most acceptable.
These are the possibilities:
1. MT is the word of God (so Jerome: Hebraica Veritas).
2. LXX is the word of God (so the Orthodox Church).
3. Both are the word of God (so Augustine)
4. None are the word of God (maybe you go with the Samaritan Pentateuch instead or something else?).
Again, depends on your beliefs and what you find most acceptable. The NT authors don't always quote from the Septuagint. In Matthew, for instance, the version of Isaiah that is quoted everywhere throughout represents no version of Isaiah that now exists. The Septuagint version of Daniel was almost entirely lost. The version of Daniel that now exists in virtually every manuscript in existenceincluding all Septuagint manuscriptsis not the Septuagint of Daniel, but is the Greek text called "Theodotion". In fact, there is a very real question whether we even have the same LXX as it originally existed. Most manuscripts of the LXX were altered to conform in some way to the Masoretic Text. And every manuscript we have of the LXX is different. In order to reconstruct what the original LXX was, scholars usually depend upon a huge amount of textual criticism. First, they assume that if every manuscript agrees, that agreement is the original LXX. Then where there are disagreements, they use surviving pieces of Origen's Hexapla and the translation of the Hexapla into Syriac (called the Syro-Hexapla) to reconstruct it.
Although I haven't decided yet what I think of the LXX, I do believe the MT is the word of God. The same consonantal text that I use every day existed at the time of Christ and before Christ. We have found copies of what is called the pre-Masoretic text (identical to the Masoretic Text except that it doesn't have vowel points or accentuation marks) among the Dead Sea Scrolls and outside of Qumran in other caves around the Dead Sea. So if there is a Christian bias, it would have to be limited to the vowel points, which anyone can ignore easily enough (if they know Hebrew).
Also, we have several witnessesincluding witnesses from the first century like Josephuswho said there were copies of the scrolls in the temple. These would have been considered the official scriptures. And they would have been Hebrew. One reason why the Masoretic Text hasn't changed since before the time of Christ (except for the addition of vowels and accents) is probably because the scrolls in the temple were used to correct errant copies. That's what Jewish tradition claims. And the evidence would seem to support it.
The only copies of scripture that are different from the Masoretic Text are those that were at places like Qumran, which considered the temple an abomination (and, thus, wouldn't have been having its scriptures corrected to the official copies in the temple) and those that were formed in foreign countries (like the LXX in Egypt). Every Hebrew quotation in every Jewish writing after the first century agrees with the Masoretic Text. Every one. Whether Rabbinic or otherwise. It is only in areas where Hebrew wasn't used as much (or where Greek and Aramaic were used more) that the Masoretic Text wasn't used. In those cases, the LXX was sometimes used. Sometimes the Targumim were used. Sometimes other Greek versions, different from the LXX, were used.