@Acolytus Mutuski is a loose cannon, so keeping her on a short leash is better for everyone. Also it's not like she considers it much of a punishment. She's a NEET otaku and thinks of her Jail cell as a "room". Yeah, I don't think her sentence length is a problem at all.
@Saronite Rockhammer isn't going to violate anyone. Remember that was the entire problem with Mutsuki and why she got jailed in the first place, she assumed that because he looked like a villain he would violate her, which he certain did not and had no intention of doing so. It's pretty obvious from all of the other characters conversations, including the "enemies" displayed so far that Rockhammer treats his prisoners fairly. For example when they were interrogating Serge (Hans' rival), Serge explicitly stated that their imprisonment was fairly lax compared to the rival countries imprisonment.
The bigger problem is that he's throwing all of the responsibility for the Japanese onto Hans. Poor Hans is never going to get the peaceful life he wants. When the most reliable Japanese person is Koushirou, the Yakuza assassin, you're in for a difficult life.