Albeit on another make of car, I've had Michelin Energy Savers and found them to be pretty good on snow. The fact they were less than half-worn would have been a major factor.
High gear and low revs always helps in snow and other slippery conditions... this keeps torque low thus reducing the likelihood of wheelspin. Sounds like your 'misbehaving' CVT may not easily allow you to achieve this. CVT aside, I have found my manual Jazz on its stock (summer) Dunlops (175/65/15) to be excellent in snow.
Given the weight of the vehicle - the wider the tyre, the greater the contact patch and therefore the lower the weight/downward pressure per square inch. This reduces potential for traction in snow on the road.
On very snowy roads 10 days ago, on two separate days I saw a motorist - probably an enthusiast -
in a car dating from the early 1940's. Big diameter wheels, narrow rubber, lazy power delivery from an 'olden-days' long stroke, low-revving engine and he appeared superior to almost everything else around him. In, around and out of a deserted pub carpark, he appeared to be driving around just for the fun of it.
