/pine,
I hope you don't have a disaster in the making. I'm not sure you have what you need for 12" on a hill if it is steep at all. A lot depends on the type of snow. If it stays reasonably fluffy, you might be okay. If it is wet and heavy and wants to pack to ice under your wheels, not good.
The extra weight of the ditch witch plus wide tires won't help if it gets slick on you. Big machines slide just as good as little ones on icy stuff, and they cause more damage when they get stopped. Force = mass x acceleration is always true.
My inclination would be to use the tractor bucket for most of it. The blade makes good ballast and would be good for a cleanup pass when set at an angle.
Be careful to not bend or break your tractor's 3pt lift arms if pushing backwards with a heavy blade in heavy snow. Lift arms are designed for pulling, not pushing.
If there is a danger of rolling, sliding down a hill out of control, or busting up your stuff, let it melt. Or, wait until you get enough air warmth that it won't pack to ice beneath your tires.