a dangerous contradiction
Welcome to the RTA Forum!
I'm sorry, but you've started your planning with an incredible contradiction.
You talk about wanting to find a safe route - and then you proceed to build a trip where you'll drive from Boston to St. Louis in one sitting - which is one of the most dangerous things you can do while planning a trip!
First of all, any route can see bad weather. The route you've picked simply is not any more or less likely to see a winter storm than say I-80 or I-70.
Much more importantly, Boston to St. Louis is near 1200 miles. That's 2 full days on the road, and you couldn't do it in 15 hours even with a police escort. You would have to AVERAGE 80 miles per hour! In the real world, you're looking at about 21 hours on the road!
Even if you stopped near Indianapolis, where your map seems to indicate, that's still a good 17+ hours of driving.
Simply put there is no way to do that safely. Your plan to rotate sleeping is extremely dangerous, as there is no way to make sure the driver stays awake while the other person is asleep. Since you don't have a 3rd person to do a real rotation, that means keeping your days on the road to 10-12 hours max, or roughly 600 miles per day.
If you want to do this trip safely, you need to add at least one more day on the road to do this trip and that's if you eliminate all of your extra detours at the end and you don't see any bad weather. If you want to include the Grand Canyon and Las Vegas, you need to plan on this trip taking much closer to a week.