If you don't carry an extra folding tire, look at a tire boot. I carry a 3 inch section from an old folding tire. A chain tool could be part of your multitool. It looks like you could maintain a 6 hour 100 miles, but look at a declining 2nd half at maybe 7 hours. Total 13 hours. The effort is not 2 centuries added together. You will be in the saddle for 12-13 hours with added abrasion and limited body position changes.
Also, bring something to combat cramping. Some people use tums. I like to use Nuun electrolytes added to my water.