1. If he starts proceedings in US soil then the US county Court will not allow you to take US citizen child to India.
2. Taking up US citizenship is not a pre-condition to take child to India. It is noticed that many Indian mothers have illegally taken minor child of parties without consent of natural father(s) from US soils to India on some or the other pretext and upon reaching Indian soils have waged women centric Indian laws upon natural father(s) making US based natural fathers take up herculian legal battles both in Indian Courts as well as in US Courts.
3. US Court will have jurisdiction if both parties submit before the county Court since natural father and child are US citizens r/w you are on living there on PR status.
4. If child is US citizen then US county Court can order its return to US soils. Ref. to a very famous case of Dr. V Ravi Chandran Vs. Vijayashree Voora about which I discussed here in this very forum in great details some years back, where the Indian Supreme Court has ordered the deportation of the wife and her US citizen child involved in a legal row with her above named Indian born US citizen husband (Supreme Court citation Nov. 2009)
5. Ideal way out from your brief could be to consult local Attorney and seek 'a just' pre-trial memorandum on child visitation - custody order(s) from jurisdiction county Court under whose ward parties US citizen child resides as per US laws.