The original autographs are long disappeared like the Ark of the Covenant. That we have what they contained is owing to Tradition, As for the Septuagent, I am unsure why you insist, with the rabbis, that only works in Hebrew are canonical. It suits their Tradition but not ours.
One can piece together the original using deductive analysis in comparing all extant early manuscripts.
The fact of the matter is that I accept that God has preserved his word through the ages. It is the most well documented book in the history of the earth.