What Jews kept in their temples is not relevant to what Christians realize that inspired. We, for example realize the Gospels and Epistles as inspired. The Jews put St. Paul to jail and ultimately engineered his execution for writing his letters. No wonder he wrote in Greek, the language of the Septuagint.
If St. Paul meant to say something like "Scripture in Hebrew" or "Scripture the Jews use in synagogues", or something similar to what you want to put in his mouth, he would have said that; he was not tongue-tied. He instead said "all scripture" -- not this and that scripture, and he said "known" not "approved by the Jews". Read the Scripture and respect it. Please. All of it.
For example, when we speak of what Paul had, we invoke a probablistic mode of analysis that asks, not what did the Roman See consider important 400 years into the future and work back from that, but what would a typical Jewish Christian apostle of the First Century most likely have in his possession, based on what we know of the Jewish Canon at that point in time. Under that model, second class documents not being treated as canonical at that time would not pass that test. We know Paul had regard for the Jewish magisterium, as he stated to them were given the oracles of God. If they had not accepted the deuteros, and we know they didn't, we would expect Paul to make an argument for their use, and also to use them, as he was very well versed in the Scriptures. But in fact everything he used, as having the force of canonical authority, was from within the limits of the smaller Jewish Canon. This makes sense. Speculating forward 400 years then reading it back to Paul is circular reasoning at its finest, and therefore completely untenable, at least to us evangelicals, who are not ever going to be comfortable with such blatant circularity.
Yes, please read the Scripture and respect it - ALL of it - because we KNOW that ALL Scripture is given by inspiration of God. If some are unable to recognize the serious and supernatural basis of such writings, so that they foolishly imagine whatever "their" religious leaders decide is "Scripture" centuries after the fact must be so, it is THEIR error to work out, not those who truly respect God's word.
There IS no argument you have that can convince me your religion's decision to include humanly devised fables, myths, vain imaginings and fallible recollections into what ALL genuine Christendom acknowledges is Divinely inspired and SACRED Scripture. I respect God too much to blithely consider His revelation could be polluted this way. However, if you feel you have no other choice but to defend what is indefensible because your "church" deemed it so, you have my sympathy. What you will NEVER have is my agreement.