I think you are right. I think he was the first to translate the Bible into German. So you gotta wonder how much of his slant was put into his translation just as all translations.
The Greek word translated as “faith” in Romans 3:28 and in many other places in the Bible is pistis. One of the two main definitions of pistis is indeed “faithfulness.” And that definition helps remove the apparent if not real contradiction in the sheep and goats parable given by Jesus. In that parable, Jesus does not say a word about faith as saving the sheep. Instead he emphasizes that the sheep did good things for others in need. These things are precisely the sorts of things that Jesus himself did or would do. Having faithfulness in Jesus or being faithful to Jesus likely entails following his example or following his admonitions, e.g., loving others. Thus, the “faithfulness” definition of pistis makes the parable more compatible with the rest of scripture that emphasizes pistis. It’s less compatible if “faith” were intended as the definition, for as you said, why would faith in Jesus necessarily lead to such admirable behavior?
Yes, I agree. Regarding pistis as ‘faithfulness’ also sheds light on Paul’s saying ‘from pistis to pistis’ - translating as ‘faith’ is difficult; but by using ‘faithfulness’ in each position gives us what probably is Paul’s real meaning - that he, Paul, is laying out the utter faithfulness of God to the Abrahamic covenant even in the light of Jewish and gentile faithlessness, and that understanding of God’s faithfulness leads us to faithfulness.
From faithfulness TO faithfulness.
Luther’s translation into German may be superior to most or at least many translations. Several times when I have pointed out specific passages in which the Greek text differs a lot from the King James translation, Mennonites who were present and who regularly use Luther’s translation, have told me that the meaning in Greek that I pointed out, was the same as the meaning that comes out in Luther’s translation. I can’t vouch for the accuracy of that statement since I am not familiar with the German language.
Saved from any sort of retributive or penal wrath on the part of God because they are all seen as righteous, from eternity. Furthermore, when they believe they are saved from the apprehension of wrath in their consciences.