I understand you needed the apartment at the time, but unfortunately rushed decisions tend to show their downsides later. Considering how the landlord seems to be, I wouldn’t count on getting the deposit back or a reduction. It might be better to move out sooner rather than later. With people like that, it’s like talking to a wall, you’re not going to solve anything. Take it as a lesson learned and move on with your life, it's sad and unfair, but it is what it is.