His argument is not that the Church has mistaken Pauline Justification these past 2000 years. It is that the Reformers understood Pauline Justification through the lens of what they were going through and that we mistakenly take up a Reformation view of Justification rather than allowing Scripture to dictate that view.
He does not view the law/grace issue though as paul has in his theology of justification, as it seems that he gives more weight to obeying the law, and being a covenant people with God then the Bible teaches, as he seems to hold more to what Judaism of the time did then what paul had to say about it!
And pauline justification is THE key to understanding the gospel of christ , correct?