Grace to you as you navigate your way out of NAR and the associated legalism. Consider my answers below:
Ephesians 2:1–10 should be the death knell for an RCC interpretation of Paul's thoughts on justification. Not saved by any works, but created for good works. Speaking to Jews and Gentiles. No Mosaic Law in view.
Variously, but mainly in two ways: a) James and Paul are speaking about two kinds of justification (before God and before man), and b) they are speaking about the one kind of justifying faith that's always accompanied by works – the works show the faith is genuine, but it doesn't *save* as the grounds of salvation. Read this to go deeper into this latter view.
jsyeo's viewpoint on 1 Cor 6 is solid. People who are actually justified turn away from sin... inevitibly. That's the Reformed doctrine of "perseverance of the saints". It might not happen now or soon, but it does happen. Whoever God justifies he also glorifies (Rom 8:30), which means the middle part (sanctification) also must happen.
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