Did Peter understand that God was moving away from Israel and the covenant promises to the Gentiles?
No. Scripture indicates Peter, for the most part, had no comprehension of God's great move to come away from Israel and the covenant promises and go to the whole world, Jew or Gentile, with the gospel of grace. That understanding came through Paul.
Les teaches that the theme of Galatians is that believers are not under law but under grace, a truth that came first and foremost from the Apostle Paul. This was an unknown tenet, and even Peter for the most part had no comprehension of God's move away from Israel and the covenant promises to the whole world, Jew or Gentile. Les notes that this is hard for many to accept, and he rejects the claim that Peter's message and Paul's were the same, calling the difference daylight and dark. Later, Peter had a difference of opinion and wrote that Paul's writings contain things hard to be understood.