In order to decide whether Yakov was happy earlier in life, we need to know what's causing Yakov's depression at the end. Is it the fact that he always lived his life selfishly and lost contact with his family, or is it that he simply lost his daughter? It seems like Yakov attitude towards his wife was the same earlier in his life as it was at the end of the story. He says that he "never" showed affection for her. This would make it seem like Yakov didn't ever live blissfully. He also says his life is "wasted" not lost or taken from him. That makes it sound like he was responsible for the depressing circumstances he finds himself in. This is all evidence that Yakov always placed his money and career over his relationships with others. He even concludes, "If it were not for hatred and malice people would get immense benefit from one another". This sounds like self-accusation, and Yakov could be blaming his misplaced attention. In this case, Yakov was never happy. He was always a misguided idiot who wasted his life.
Yet, at the same time, we can make an argument that Yakov did have a enjoyable past--only he's repressing it. We never really know whether Yakov accepts the fact that he had a daughter who died. We know he accepts his grief when he plays the violin at the end, but we're still not sure if he knows why he's grieving. All of Yakov's unpleasantness--that malice that he believes ruins relationships--could be a symptom and not a cause. He could be depressed because he has lost his daughter, and now he's inflicting the pain he feels internally onto others. His obsession with lost money and work could be the misplaced feeling he has about his lost daughter. Think about the violin playing; it evokes such a powerful emotion from Yakov because it's played plaintively. It makes more sense that Yakov would respond to the music because of a sense of grief and not a misspent life. When Yakov goes to the river and realizes that life could have been different, better. He imagines positive images like the geese coming together or the river filled with boats. If this is what Yakov hasn't been seeing in his life, then the music which would remind him wouldn't be plaintive. It would have to be symbolic of the life he had chosen to turn his back on. Really, it makes more sense that the music would reach Yakov because it's reminding him of a painful memory which he's trying to repress. That's the best argument I can make for this reading. There are others but it might become tedious if I listed them all.
I was hoping I might make this problem a little more solvable by the end of this post, but that's not going too well. I'll give one last possibility. It could be both A and B.