Here is my finally successful follow up in case it helps others.

I gave up on the Dec/Jan idea and resigned myself to a two week trip. I targeted covering at least one holiday to save a vacation day.

Alaska also crossed me up as I missed that little seat icon that means mixed cabin so all of the fights I thought were business were really coach across the pacific. Frustrating but lesson learned.

I targeted Alaska and United miles trying to find a southbound flight leaving on Fri/Sat and a northbound return on Sat/Sun/Mon two weeks later to make the most of weekends. I was also doing my best to not route through Asia to save hours, so focused on Qantas, Fiji, United and Air NZ. Probably ran 1000 searches and finally ended up with:

YVR-SYD on Saturday 7/1 (Qantas booked with 55K Alaska miles & $41)
AKL-SFO on Monday 7/16 (United - topped off account with Chase UR to 70K & $42)

I would have preferred Spring/Fall, but took what I could find.

I managed to work the YVR flight back to SEA but couldn't get availability all the way back to DTW. Also tried to build SFO-DTW in, but nothing. The only thing with J available was to YYZ but would have meant another night in Toronto.

I still need to book the west coast open jaw, but that looks to be $500 coach or $1000 first - not much value in cheap awards. I'll head out Friday night and stay in SEA to avoid missing a flight. I have Delta bump credit and Amex PRG gift cards so that works well. Still need to build an itinerary to figure out when/where to hop from AUS to NZ.

I figure I got about $6000 in value for 125K combined Alaska, United and Chase UR points. Not gonna complain about 4.8 cents per point!

Thanks again for the help.