1:15-17 (A) What does Paul mean that God separated him from his mother's womb and called him by his grace - is this not teaching that Paul was predestined to salvation?

No! This simply means that Paul was set apart by God, like every believer in Christ is while still in the womb, for service unto him (cp Eph 2:10).

This is the calling of every New Testament Christian. We are all called to be ministers of the gospel of Jesus Christ.