I'm interested in visitations. How can my son come in USA without USA passport?
Your son cannot travel to the USA even with US passport but without mutual consent of both parents. This is why I think it will be best option is traveling to the USA as whole family, and starting legal proceeding in the USA, under US jurisdiction. You have very limited options in the Russian court. The Russian judge never let you travel with child to the United States because there are no option to return child back (Hague convention of 1980 doesn't work between Russia and USA).