If there are no Jews or Gentiles, then from the perspective in Christ it's not a "goy" because it's not "Israel" either. From the perspective outside of Christ it's still both.

You say you're familiar so I'll only allude to the fact that Israel has two applications, national Israel gets national blessings and responsibilities, and spiritual Israel gets spiritual blessings and responsibilities.

As to Sabbath I'll let my words and others' suffice for now.