Charles:
To add to what you've said above:
In the letters of Paul, he quotes from or makes clear allusions to the Tanakh 111 times. In these quotes and allusions, he references the Torah 46 times, the Prophets 42 times, and the Writings 23 times (41% Torah, 38% Prophets, and 21% Writings). The majority of these quotes and allusions (75%) are from the Torah, Isaiah, and the Psalms.
Yeshua, Himself, referred to the Psalms as "written in your Torah:"
John 10:34: Jesus answered them, Is it not written in your law (Torah), I said, Ye are gods?
Yeshua was quoting Psalm 82:6, and yet, here He is, referring to it as "written in your Torah."
It is interesting that when the manuscripts at Qumran are tallied, the three books most represented are Deuteronomy (27), Isaiah (21), and Psalms (39). This would indicate that Paul’s use of the Tanach fits into the general perspective of the 1st Century Judaisms.
In literal terms, "Torah" refers to the first five books of the bible, but in very real terms, "Torah" refers to the *entire* volume of scripture, because every other book was tested against the Torah to determine whether or not it was, in fact, "God-breathed." Any book which did not agree with Torah was thrown out.
As you pointed out, the Tanakh was the only "bible" in the Apostles' day. For Christianity to claim that we are no longer under "Torah," they are claiming that the entire "bible" of the Apostles had been rendered obsolete, and that they began writing their own "scriptures" to replace it.
Shimon