That's 2,000 miles, give or take a little, in 3 days? That would call for 660 miles per day, more or less, which will take you AT LEAST 13 hours drive time each day. And that assumes no bad weather, which is really pushing your luck IMHO.
That's also taking I-40 to St. Louis, and that would be absolutely the farthest north route I'd even attempt at that time of year. Of course, all bets are off if you run into snow.
You don't mention what, if any, experience you have driving in snow. If none, I highly recommend flying and leave the RV at home. As for Vail Pass, no way, forget it towing an RV. Even if you were an ace driving in the snow.
