Ugh, what a hard situation. Did you indeed realize that moving in with his parents early on meant forever? Was he clear about that? This is difficult because it does sound like a cultural thing. Personally, I would not want to live with my husband's parents (or mine---- as in I want to be an adult couple who has my own life and home) but that is my culture. Can you compromise and live nearby and see them/help them often? I think your own happiness should matter. But I am not sure what to tell you if your husband is unwilling to make any changes to this subject. So sorry I'm not of more help.
I hope I'm not seeming impolite to ask, but is this an Indian family? The son choosing his parents over his wife is something seen on this site in letters from women in India and Pakistan and Muslim countries but not so much from women in Europe or the U.S. I ask because there are such big cultural differences that any advice I might give to someone in the U.S. would not apply at all to a woman in India.
I would seek out a female therapist and talk over the situation, and a female lawyer who handles divorces to talk about unexpected consequences (you don't want to get sued for abandonment). If the therapist is in your own hospital all the better, as you will be able to see her often. If leaving is in the cards (and you are fortunate that your job will allow you to support the children, so many women in your position can't leave) you should check with your lawyer to see if there is any way to clearly leave the door open for your husband to come too, to establish that you aren't abandoning him, just the uncomfortable living situation. (And perhaps he will decide to come for good, since your home will be peaceful and serene and his home with his parents will not be so much.) If you are in India, there are those extreme stories that one hears about how in-laws harm their daughters-in-law, this is one of the reasons you should have a counselor (one psychological, one legal) to talk over all the possible ramifications of your actions before you do anything.