I grew up in northwest Iowa and have lived and worked in a lot of snowy places. Obviously, all-wheel-drive is preferable, but a well-balanced rear wheel drive car with antilock brakes and stability control works pretty well.
I do not care for front wheel drive cars, particularly stick shift front wheel drive cars. They tend to be front-heavy which makes for unpredictable cornering.
Four winter tires is better than four all-season tires, and four all-seasons is better than mis-matched (two of each). One advantage of keeping a set of winter tires is that you can put them on steel or other cheap rims that can get salted with no heartache. However, if you don't need to get out before the snow plow, and if budget and tire storage are problems, look around, I think you will see that most of the passenger cars in Michigan are driving on all-season tires year round.
As for added weight, OK to help you climb that icy hill, but generally no. You don't want your rear end wanting to pass your front end when you try to stop on ice. I have added weight only to balance out front-heavy pickups. If you want to carry a couple of sand bags, carry them on the rear seat floor and transfer them to the back of the trunk only when you need to make it up a steep driveway.