The main problem was the cloud ceiling which was low at JFK for an NPA and they couldn't do ILS. The other failures like APU, autoland, double RA are not significant. They chose their regular alternate EWR as the ceiling there improved 400ft.and trend showed further improvement. EWR has LNAV/VNAV approaches on both sides of the runway with 400ft. Ceiling. Once committed it's natural to feel anxious about the actual ceiling prevailing and whether they would see runway environment at minimum. Possibly they busted the minimum. With GPS PRIMARY should not be that hazardous.