This is probably more info than you asked for but thought I should share.
So we've done Yellowstone from Kansas and while not nearly as far as you have to travel we did do Custer, SD to Yellowstone to Mt. Hood to Oregon coast then back to Kansas this summer. Our average travel speed with stops for fuel, meals and toilet breaks was 55 mph. Highway speed was 65 mph. We averaged 12.02 mpg with a 2013 GMC 2500 HD towing a 10,500 lb 5ver. These are real numbers based on my actual experience. From Jacksonville google maps shows the south entrance to Yellowstone at 2208 miles. Your trip, in order to make it in two weeks will require 3-4 days to get there depending on whether you want to drive 10 hour days or 13 1/2 hour days. I've done both, while I don't mind those hours my wife hates more than 10. Assuming you're willing to do the 13 1/2 hours you'll need 6 days round trip. that gives you 8 days of Yellowstone and anything in between. St. Louis Arch is kind of cool if you've never done it. I wouldn't do it twice. I highly recommend Rushmore and Crazy Horse, Crazy Horse is better IMHO. We stayed at The Roost Resort in Custer, S.D. After that you can hit Devils Tower as a side trip to Yellowstone without spending the night. If you're not up to the 13 1/2 hours of driving and opt for the 10 then it's 8 days round trip with 6 days for Yellowstone or anything else. You could spend a couple weeks at Yellowstone and not see everything. Prepare for a lot of driving. The Yellowstone Grand Loop is around 100 miles. Depending on where you stay it's a 1/2 hour to an hour drive to see anything. Start early in the morning. We entered the park each day at 5:00 am and was back at the camper by 2:00-3:00 pm. This allowed us to avoid most of the crowds and made for a much more pleasant experience.
Getting back to your original request I would suggest the 10 hour days and then just spend 5-6 days touring Yellowstone. With two weeks I would forget anything else.