VM/EX-P is a good combo, although you might want to consider EX instead. my avatar is of the VM/EX-Px2/CMW combo on my blue Mach1, yet the EX x3 looks the same.
i don't think you'll need to top it off. if you do, use a pure wax like Meg's #16 or Natty's or s100, not a synthetic wax, i am assuming you're asking about a synthetic wax.
VM is great on any exterior part of the car. it's great on chrome, side and rear windows, trim that's not textured, pretty much anything the bottle says it can be used on. not sure about the wheels though.
and the steps are glaze, sealant, then pure wax (optional). i haven't heard of people going synthetic wax, glaze, then caranuba wax.
as far as durability in the winter, i have no idea as i don't have those conditions in hawaii. i've heard people prefer Zaino or the Klasse Twins for those types of conditions, and have sucess with them over the winter. if you're looking for durability, you might want to consider one of those two, like the Klasse Twins as it is slightly easier to apply. the Zaino you'll be mixing things, and it might take some time to get used without wasting it.