After the third (or fourth? I lost count! LOL) rewatch, I'm not entirely sure Rajan is collaborating with the police. He came home from travel and said nothing until he opened his friend's present, when he took some time to think and then told about the collaboration thing. Hum. Perhaps the gift was a coded message for a menace and decided to invent the collaboration cover story in order to save Kala without confessing his involvement with the bad guys? I mean, we already know he was doing bad things shipping the expired drugs. We also know that he was arguing to someone on the phone and he said to leave his family alone. So, seems like he was being threatened for stepping out from the expired drugs business (or other dirty business).
It's just a speculation, though, based on the fact that my thimbs pricked when I watched (again and again!) that scene.
Although it would certainly be easier to support Kala if he was a bad guy, I've always thought that good or bad, if you don't love someone, why should you stay with them? Plus, I ship Kala and Wolfgang together since the beginning, because, among other reasons, there a fantastic example that love is blind and takes no account of tastes, morals, cultures, etc.