I'd personally plan for a "diversion" to SYD - more options, but then as Nick said, you'll have problems getting into OOL as QF mainline don't fly there at all any more. Limiting yourself to one option (via BNE) reduces the odds somewhat.
Feb is low season ex-AU, but in this day and age what was true in the past isn't necessarily so any more. Midweek has always been easier in my experiences on trans-Pac than the Thu-Sun spread.

You're also forgetting the obvious - AirMike into CNS from GUM. As it's all in-house, you'd be able to get a better idea of loads etc. CNS-OOL options would be QF via BNE then land, or if your own CO flights into GUM and CNS look good, then get in for a cheap web special on Jetstar, QF or VirginBlue.