As for House names, I think we should rather go like this :
Rennes = Bretagne
Toulouse = Navarre
Reims = Either Champagne or Lorraine. The latter would particularly work if we include Metz into the realm fast.
Dijon = Bourgogne seems fine.
As for titles, Seneschal sounds fine for the title of Chancellor
As for the assembly, the assembly of the second-estate was established much latter. At the time, such a thing didn't truly exist but a Conseil Royal (royal Council) or Conseil du Royaume (Council of the Realm) or High Council (Haut Conseil) would be the nearest thing we would have with the members dubbed Conseillers (Councillors).
Edicts should be Edits
Constitution would be Charte (the term constitution didn't appear until the French Revolution).
Amendments should be Proclamations.
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