You should look at the weather report for the time you are going. I'd hate to drive during a snow storm in a XF, and you'll be going through a lot of road miles that have the possibility of being snowed on. I know you are used to driving it at home in the snow, but I'd hate to get stuck in a snow drift or something far away from home.
The gas issue, just don't let the tank get to fumes. There are a ton of gas stations on the way down, don't pass one up when you are getting low, that's all.