Some of the people I go with who come from Boston take maybe 4 hours, weather considered. Vermont is pretty good about keeping the highways clear during the winter. I drove from West Dover to Rutland on shitty Highway 140 on the weekend of Feb 27th this year. That day, Mount Snow got smashed with almost 20 inches of fresh. I made it fine in a front wheel drive compact with all seasons and no chains, though I wouldn't prefer it. The interstates should be ok, although that weekend, Massachusetts decided not to clear 91 north of Springfield.
I would allow yourself 3 hours driving time, minimum. Your suggested time table will be cutting it close when you consider time to check in, check bags, go through security, walk to gate. I'd stick with the 4:55 flight and leave the lodge around 1 PM.
Also, Killington isn't so bad. Check out The Stash while you are there and most of the crowd on Bear are pretty easy going. Stay away from K1, that place gets packed on the weekends. Ramshead can actually be very good for turning in laps, although the only thing over there is the little Timberline terrain park, it's actually pretty fun. It gets very empty 8-10 AM, lunch time and again aruond 2:30 PM.