We need to know exactly what battery is installed.
If some other than standard Odyssey battery is installed, you're on your own.
As someone who does regular super cold weather starts, (2200 engine) effortlessly, with the recommended Odyssey PC625 battery..... I'd use nothing else, despite battery spec promises.
I also get ten years out an Odyssey before I change it, and it's still starting just fine every time, summer and winter. Ten years is my limit, not the plane's limit.
Winter plug gap = true, there is such a setting and from experience, it does make a difference. 0.020" is indeed the figure in the manual.
NGK D9EA plugs, (we assume)
Coil gap check = true, check it. I found a cardboard manilla folder piece is the exact thickness. (digital micrometer used)
THICK OIL = could be problematic. I've only ever used 15W multigrade oil, all year round.
CHOKE full on, throttle full closed = true. (assume choke is fully opening.)