I believe Ben was lying about how Nadia died just to use Sayid for his own ends. I think she really did die in an unrelated car accident. Sayid should know to check his facts instead of taking Ben’s word.

Also, I don’t think Jack is showing signs of addiction yet. I believe he is having appendicitis or something of that nature. He looked worn out and in pain throughout the entire episode. I think his joke was simply a moment of irony that only we, the audience, can understand.