...Hah. What's the old saying "the mind sees what it chooses to see"? I looked around for some translation that mentioned Rosa's Father as a Dark Knight, but everyone I found just says "Knight", I guess I assumed it was Dark Knight and not a Dragoon, but since that's called a Dragon Knight in Japanese it would make sense that it would be a "Knight" as well.
My mistake then.
You are also right about the villager, but it wasn't in regards to forcing soldiers to use the dark sword. It was that the King was even allowing them to use Dark Swords, here's the literal line from master translator Tomato: "In Japanese, it?s more like, ?Teaching soldiers the way of the Dark Sword! Just what is the king thinking?!?"