Need help to get back my deposit

Dear expat community

When I moved to Denmark about 4 months ago, I had problems finding a house like everyone else. So I rented a room a outside the city in the suburbs (Dragor). I lived there for about two months and moved out quite spontaneous when I found a great room in the city (that was in the middle of October, I already paid the rent for the month then). My problem is now, that my landlord only wants to pay me back half of my deposit (the one for december), even though he already found a new tenant. He claims that, even though after cancelling my contract, I still have to pay my rent until the end of next month. From all I know this is true, but only if he doesn't find a new tenant until then. So as it looks now, the landlord just get paid twice in November (my November deposit and the rent from the new tenant). Does anyone of you know if this is legal and if it isn't, where I could get legal advice? Can I put some pressure on him (some kind of government agency maybe?) to make him pay me back somehow?
Then the second thing I realised after I moved out: I believe that he charged me way to much for electricity and water,  1000 krona per month. In my new room I pay 400. I'm also not sure if this was legal, any ideas about that? It's not very much but still it pisses me off, especially because I know he has a lot of money (he owns about 6 houses) and still he tries to ripp of students and other foreigners like me who are not sure about their rights as a tenant in Denmark.

Thank you for your help and best wishes
Yanick