Are Nathan, Rukmani and other characters responsible for their own condition because of the decisions they have made throughout the novel?

hmm... that's a hard one to answer, because it really depends on your view of autonomy versus fate. I think that it would be hard to say that Nathan, Rukmani and the other characters are responsible entirely for their condition. Because of the terrible floods, there lives are almost entirely ruined. It is hard to blame the rains on the family. However, some of their decisions do negatively effect the family. For example, Rukamani's son was killed for trying to steal a pelt from the factory where he worked. That was his decision. Overall though, i would say that though they are responsible for their decisions, they also had a lot of things that were out of their control.