If time is a problem then think again about the Southern Tier, from the other side of Kent take the 190 straight across Texas, and beyond , great road cuts off a fair few miles and hills. The deserts are not a problem on the ST as a little bit of planning and extra water will see you safely through, the distance between places is never that big. I planned to wave down an RV if ever I ran out of water but never needed to and only occasionally did I have to haul a full gallon with me and then didn't really need that much but gave me confidence having it along.
PS if you ride the 190 in Texas look out for Red Chilli burger bar in the middle of no where best burgers en route. Gets a bit hairy around Austin but by making up the route I by passed this on some unmade back roads.