Process to get maintenance for son if MCD done under pressure

Dear Sir, My case details; Marriage - nov 11, NRI husband, SEPT 14 he filed false case under 304/506/504 of IPC , accused me, my family (Parents, Siblings) as his father expired of natural death, heart attack but conspired this case against me to get divorce on MC. MCD filed in Oct 14, agreement includes clause to withdraw 304/506/504 case and in my part he added not to make any claim wrt to alimony or child maintenance in future. gave certain minimal amt against streedhan, maintenance all. Divorce is already done in Oct 15, I signed under pressure , no other way left. My question, I am able to earn Rs 35K in Noida and have to manage Home rent (10K), Son's school and creche (8k) and other misc expenses eg Ration/ utility bills, medical etc. Husband earns Rs 2.5 lacs in indian currency as he works out of India. is there any way out / law / clause which can help me to get maintenance for my son only and his future education at least ? in case , in reply to my Maintenace case, he files Custody (although he does not care for son at all, otherwise would have separated making some decision for son's well being) to harass me, what are the possible decisions which court can take. son is now ~3 years old. Verbally they are not at all cooperative and ready to discuss, please advice for me to get justice. Thanks for your valuable advice.