Answers on Ephesians 3

6. είωαι is the abstract thought; they were to be so.
8. It is a present sense: what he was accounts for his sense of it. Compare 1 Cor. 15:9.
9. The apostle everywhere speaks of a mystery which was in the counsels of God before the world and not revealed before the cross, when the responsibility of man, the first Adam, reached its climax (save Christ's intercession for the Jews on the cross).
21. Yes, it uses elaborate expressions to give continuance and forever.