I cycled across Canada back in the mid 90s with my brother and remember Saskatchewan well. Mind you it was early summer, but cross winds and trucks coming too close were all we had to contend with.
Back to your i3. Consider some sort of insulation or cover for the charger if the car will be outside. When its charging and it snows it can potentially freeze to the car. Forcing it free can damage the locking solenoid, then you can't charge it. On models state-side, then they are different from European models in how the charger connects and locks, but something to consider.
I made something very simple from polystyrene that you use to cover outside taps. Very effective. More details here: https://www.bmwblog.com/2016/02/21/bmw- ... now-cover/
No idea how much salt they thrown on your roads, but if the car has diamond cut alloys, then save them for the summer months and opt for powder coated alloys and winter tyres, otherwise I suspect they will corrode under the clear lacquer in a couple of years.
Use the REx engine. It will fire up periodically which is automated, but regular use, say once a week ensures the engine gets hot (which I'm sure it will given your distances), helping drying out any moisture and just keeping it lubed and ticking over.
2015 i3 REx, 60ah, solar orange. Reversing camera, leather interior, sunroof, park assist, professional navigation.