Interesting piece.
I would suggest that two other issues are not addressed:
Church Tradition — Catholics and Protestants see Mary and other Saints differently. Many church teachings beyond the Saints can also be considered traditional rather than scriptural. This is not a minor point.
Priesthood of all believers — again, there is a sharp distinction.
Both points could be considered areas of “intercession”. Do believers go directly to the Word and directly to Christ? Or do intermediaries play a valuable role? Can Mary intercede? Is confession to an earthly priest valuable/necessary?
The basic rift is pretty wide, IMO.
If, like Luther, we go back to Paul, apostle to the Gentiles...the Reformation succeeds. Spend a year in Ephesians and Colossians, have your mind renewed and transformed, then revel in the above and beyond generosity of God in his Son! His riches are “unsearchable”.
There’s a lot more to it than those three “foundational principles,” to which I think no orthodox Christian objects.
What is "the faith that was once delivered to the saints"? It is the gospel of the grace of our Lord Jesus Christ unmixed with the law. It is "the just shall live by faith without the works of the law" (Habakkuk 2:4; Rom 1:16-17, 3:20-22,28; Galatians 2:16, 3:11; Heb ).
It is the gospel that Paul preached in Acts:
Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses.Acts 13:38-39.