The Hebrew word translated "Country" is Sadeh. It does not mean "Nation". It means Fields, Farmland, Fertile ground, etc.You have proved nothing.
Plus I don't use the Masoretic Text.
My Septuagint doesn't say plains of Moab. It says country of Moab. It was MOAB either way dude!
Here is Young's Literal Transaltion....probably the best:
[Ruth 1:1] And it cometh to pass, in the days of the judging of the judges, that there is a famine in the land, and there goeth a man from Beth-Lehem-Judah to sojourn in the fields of Moab, he, and his wife, and his two sons.
Use your common sense!