Ephesians was the widest circulated document of the apostles. see text notes on 1:1; there was no destination named in the earliest copies.
2B-3A are emphatic that there is one entity that receive the promises and blessings of God, those who are believers. the thing hidden from Judaism is that this would not occur by the Law. It is now known to be through the Gospel.
Judaism did not have any doubt that God was going to impact the nations. It was everywhere in the prophets. But the Law embeddedness in Judaism prevented them from seeing how, which is why through the Gospel is the most important phrase in Eph 3:5,6. Torah was one of the three parts of Judaism's 'trinity' (Yahweh--'eretz--torah) and God "had" to do anything he was going to do with the nations through those other two.
That is Judaism's view, not the apostles. Last I checked, we are following the cue of the apostles, right?