I will only critique your theology here, for men like Moses, Paul and Peter were far from great sinners. The degree of iniquity of sinners and their judgment is based upon the degree of sin relative to the light and other aspects of grace given to them, and motive in cases where that applies. Peter was trying to defend the Lord He loved (and likely was aiming for the head). Moses killed a man who was abusing the people of God, and Paul in conscience toward God was punishing Christians (which is why he could say, "I have lived in all good conscience before God until this day:" Acts 23:1. "but I obtained mercy, because I did it ignorantly in unbelief." (1 Timothy 1:13)) In contrast to which is a man such as John Newton, who, having read the work of Christ-rejectors, not only did the same but tried to subvert the faith of others, and not in conscience toward God.
I hear and agree with most of what you say. I only ask
“Did Jesus ever teach the “Just War” concept?
I don’t think He did? But I reserve the right to be wrong.
No. They were sinners. ALL have sinned and come short of the glory of God. They were forgiven, but they did indeed sin.