I have a floorjack and full-size spare in the trunk. The jack stays put in the spare well, and the wheel doesn't move too much on the carpeting. Also running winter/summers as well.I put some winter tires on the OEM 18s that came with my '18 GT. I also put a couple of sand bags in the trunk. Even with all that, I tried to avoid driving in the salty slush left behind after the plows and salt trucks do their thing. When it came time to swap out the winter wheels for my summer wheels, I wrangled the sand bags out of the trunk and discovered that some aggressive cornering had flung a bag against the subwoofer and cracked the plastic grille. This winter I'll try to secure the bags better.
There's a winter severity index for road maintenance that takes into account amount and duration of snow, freezing rain and blowing snow. The higher the number, the more severe the winter driving conditions. SE Indiana ranks in the '20s, SE Michigan (like SE Wisconsin where I am) ranks in the '40s and SW Michigan ranks in the '70s.