I agree with the others. You're trying to do too much. Your intentions are good, but save some for another trip or two... Or three.
3 days at Yellowstone? Which 50 percent do you NOT want to see?
For my positive comments, make reservations for campgrounds ahead of time. Especially that time of year. There is peace of mind knowing that there will be a spot for you at the end of a long travel day. We did a three month loop of about 1/2 that size, and I spent almost every night searching for the next campground. Don't travel more than two days in a row without having a "day off". Allow more time than you think you will need for the destinations, and extra time for problems. You WILL find things that you want to stay and see along the way that you didn't count on. Don't travel more than 300 miles a day if you can help it.
BREATHE and enjoy the trip instead of trying to prove that you can do it.
Good luck!
