Your boyfriend should have moved his car so the plow guy could do his job.

You are paying to have the driveway sanded and yet his car is in the driveway. So either the driver takes a wide berth and a big section of the driveway doesn't get sanded (and boyfriend slips and falls on the ice going to his car) or the driver tries to cover as much driveway as possible.

On the other hand, I wouldn't consider you difficult if you told the plow driver "hey, I know it is hard to sand/plow when there are cars in the driveway, feel free to just give a wide berth to the cars rather than trying to sand right up to the cars." It is all in how you say it and how often you say it.

Just wondering, do you tell your boyfriend how to manage his house?