This is first and foremost a legal question that requires a specialist in these marital matters. You will need someone familiar with the laws of your country and (very likely) with an international perspective as well.
Psychologically, your needs sound clear and understandable. It seems little wonder why you have separated from a man who is worried more about what others think than the reality of the situation. It also seems he has little empathy for his child’s mother’s needs.
The difficulty here are the legal issues. Naturally, I cannot render a legal opinion, but getting a consultation with someone who understands the complications of a mother wanting custody, who lives abroad while your son and his father and extended family live in India is essential. This must first be decided what is fair legally, then the psychological need of the situation can be more fully determined.
In the United States there would often be a psychological evaluation of the child and perhaps the parents as well as part of the legal process. This is why working with a knowledgeable lawyer in these matters with an interest in your specific concerns would be a necessity.