3) If going with revenue, is it worth the extra $400 to fly NZ economy over UA economy on the way home?
One thing to consider is UA has one flight a day to the US, where as Air NZ has multiple flights to multiple cities. I greatly prefer Air NZ over UA as the service is sooooooo much better. If something happens, UA will have no problems having you wait another day or so to get back home where Air NZ has lots of options.