This may be a cross-cultural issue I don’t entirely understand. From my point of view, the problem isn’t with your in-laws. The problem is that you and your husband haven’t worked together to draw boundaries around your own family.
The two of you are letting the older generation make decisions that, from an American’s point of view anyway, aren’t their decisions to make. I understand that the grandparents want to spend time with their child and grandchild. But I can’t imagine relatives announcing (not asking) that they will stay for months at a time in an already crowded apartment.
I strongly urge you and your husband to talk seriously and calmly about to what extent you are going to continue doing things that are perhaps traditional in India, but are not at all the way western families operate. From an American point of view, you and your husband are adults, not children who need to do whatever his parents think is right. Your in-laws can only come to visit if the two of you let them. People can only stay with you as long as you agree to let them stay. Your in-laws should not have the power to decide when and for how long you will visit your own parents. It’s your husband’s job to tell his parents to treat the wife he loves with respect. It is your job to calmly but firmly tell them that their insults are not appropriate. But those are all American responses to their behavior.
It doesn’t have to be one way or the other; Asian or America: You can decide on compromise positions. You may have to make changes gradually. As examples: You could limit visits to a month a year or state that relatives can certainly visit but they need to stay in a nearby hotel. You could decide to alternate visits between his family and yours to make things fair and even. You could ignore your in-laws dictates and decide your own travel schedule so that your family gets to spend as much time with you and your child as your in-laws.
Change is never easy. But neither is the current situation. You are caught between two value systems — the one you were brought up with and the one you are living in now. I hope you and your husband can figure out how to balance the two, even though his parents probably won’t like it.
I wish you well.