Please keep in mind when posting a Headscratcher that this show is infamously and intentionally anachronistic and historically inaccurate, and that fact alone answers many questions.
- Why does Mary act like her having a child is solely for the benefit of France? She needs an heir to stabilize her own throne in Scotland just as much. In fact, having any child is more likely to help Mary in Scotland than in France; if she were to only have a daughter, that daughter would not be in line for the throne of France (with France practicing Salic Law, which would not allow women to rule), but she would be heir to the Scottish throne.
- Lord Castleroy is stated to be the son of a Habsburg, which implies he is a wider part of the House of Habsburg, which at the time ruled in Spain and Austria (The Holy Roman Empire). Even if Castleroy owned land in France, how is it possible that the French government has any power to take away his title which is likely not French to begin with? And his fortune seems to be mostly set up in trade which apparently works out of another country? As the wife of a foreign noble, Greer could have been banished for being an accessory to treason so to speak, but she, nor Castleroy, would hardly be ruined outside of France in any sense of the word.