Playing classical music in utero will not influence your baby's brain development. Eating oily fish is good for you and I'm sure a balanced diet will do no harm.
Your baby's genetic potential for intelligence has already been decided. Most of the rest is down to upbringing and opportunities and parenting. That doesn't mean he needs to start violin lessons at birth.
I have no PHD or masters either. I personally don't think that makes you less intelligent. You could be just as intelligent but decided to use your intelligence in your job rather than staying in education.
No, there isn't any pressure. Just chill and let your baby be the person he is meant to be rather than thinking about hot housing him before birth. He won't need the kumon shit when he is born either. Most newborns are more interested in feeding, filling their nappies, and sleeping and generally can't be arsed with kumon.