Get to Van Horn tomorrow, and go to bed early. Get a pre-dawn start the next morning, and push myself to make the 91 miles to Fort Davis (the backup plan if I'm not making good enough time would be to camp in Kent). See the Fort Davis Historical Site the next morning, if it's open on Sunday. On Monday, ride 54.5 miles to Marathon (FWIW the map says there's some kind of "cowboy poetry" gathering in the preceding town of Alpine). Stock up on food and water, get an early start the next morning, and ride to Sanderson. The next day would be Comstock (see the Seminole Canyon State Historical Park if possible), and the day after that Del Rio (see the Whitehead Memorial Museum).