Others have made very valid suggestions for what you want to accomplish. The bottom line is, from Mesa Verde to go east, without going south, and without going up to 10000 feet (sounds like one of those math questions!) is really not doable, practically speaking.
Wolf Creek Pass has a reputation...from the past and from a popular song from the past. CDOT has made substantial improvements to that pass over the years, and RV'ers and commercial truckers go over it all the time. That really is the most direct route to take to get to the Great Sand Dunes.
The only way I know of to NOT go over any 10000 foot passes and not go south would be a very, very circuitous route north through western Colorado into Wyoming and then down along the Front Range and the I-25 urban corridor back down to Walsenburg. This is really not practical unless you want to see a lot of western Colorado and southern Wyoming.
Take US 160 over Wolf Creek.