回複：回複：我該賠 這筆錢 嗎?

Cannot understand why such a small claim (civil law suit) would lead to arrest warrant. At most the court will send you a summon if the landlord's BF would really try to sue in the small claim court. But that does not necessarily mean the court would make the judgement that you should pay $400. He must prove the lost worth $400. So you might be able to negotiate with him for some compensation.

Good luck!