1. When you made the reservation were you guaranteed the Mercedes or that class (similar)? If the former, you have a complaint. If not, you don't. The fact that you made the reservation to get the Mercedes doesn't matter.

2. The fees are apparently in the contract which you signed. If you didn't like them, you shouldn't have signed.

3. You admit that the carpet was dirty. Not sure if Eur 60 is appropriate for a carpet, but it's apparently the cleaning fee and you owe it. Again, was it disclosed in the contract you signed?

4. Many European companies require a FFP card. Those points cost money and there is a lot of fraud out there. Not suggesting that you committed fraud, just that there is a lot and asking for the card is one way to reduce it. If you want the miles, carry the card.

OP really has little to complain of other than perhaps a rental which didn't quite meet what he thought it would be.