Dear Megan, towels and bedding are provided as you can see in the describtion of the listing. So there is no extra fee for towels and you did not pay an extra fee!
I checked the invoice again with your husband Rob, when you arrived, and he found out that everything was correctly. There was no good dollar exchange rate for you.
First you booked for six guest. Then you planned to bring your friends with you and you had to book in ten guest- and this is why you had to pay more.
Airbnb always takes the fee in percent from the full amount, and this is why you had the feeling there would be an extra fee- but this was no extra fee for me - it was Airbnb fee.
And it is true, there is a new law in Germany: it is from November 2015 and is called "Bundesmeldegesetz, Meldepflicht gemäß §§29,30 BMG".
The Centre for German Legal Information offers a comprehensive , freely accessible database to German law in English.
Every German Host on Airbnb, Holidayhome or Hotel in Germany has to do a registration of the guest, controlling the ID Card/Passport and sing in, and the host has to do this face to face.
So this is the reason for the check-in with all guest with all ID-Card/Passport.
This are not my rules, this is law in Germany and unfortunately I can´t change this.