Thank you for your hard work!
Because I am a language nerd, here's a a correction and some further information. A count's estate is a county (that's where the term comes from) — last I checked, "countdom" is not a word in English. In modern English, that "-dom" ending is usually used for things that aren't concrete or don't have another term for the domain held (e.g. "martyrdom" and "kingdom"). (So a monarchy ruled by a king is a kingdom, but a monarchy ruled by a prince is a principality.)
Basically:
Archduke / Grand duke — archduchy / grand duchy
Duke — duchy
Marquis / Marquess — marquisate / marquessate
Count / Earl — county
Viscount — county / viscounty
Baron — barony
Baronet — baronetcy
Other terms usually have to do with specifics of the domain and how it's held (e.g. an earl's "shire," originally).
Additionally, translations of this series and the novel both use duke and marquess where the terms should, according to contextual details, be archduke and duke (since, when inside another nation, archdukes usually have royal blood and are not numerous (so the Fredricks), where as any nation with internal duchies has multiple and many nations skip the rank of marquis entirely). I don't know if this is caused by a translation error (and lack of information) or was intended by the author, however.