Lots of good advice. I will chime in as our family does 2-3 long road trips per year.
I love in Socal and my wife's family live in Tulsa. It's 1425 miles each way. I also went to college at OSU. I have made the drive more than a dozen times and experimented with leaving different times of day/night. Have done it nonstop more times than I care to remember. That is about 20 hours of drive time and 22 hours total with food/fuel breaks. I highly recommend against this as you are a mess for several days after and it really is not safe. We tend to drive a 1000 miles and then stay the night and do the rest the next morning.
I assume the 15 hours you mentioned is from CO to 'sota. What we have found that works best if we want to drive a long distance in one day is to leave very early in the morning. We tend to leave at 1:30am. Your driving in the dark in the morning when you are awake then you have about 11-12 hours of daylight to drive when it is easier to stay awake and maybe a little bit more in early evening. We've found that the more night driving we do the more tired you get, quicker.
As mentioned earlier, absolutely reserve a hotel room at a cheap place. There are too many motel 6s in every small town that are with the $70 for 7 hours,of sleep. Do not stay in the bed ofmyour truck. For safety and sleep sake, don't. The noise of other big rigs, cars and motor homes passing right by your tailgate and the interstate being 30 years away, you will not sleep. Also, the route your are traveling is bound to have either high heat or lots of rain or both. Trust me on these.
What I take. I have a large 40"x18"x20" poly tool box with gear and supplies for road trips. Inside I carry heavy duty 20' long 2/0 jumper cables, 6 road flares, full change (7qts) of 0W-40 and filter, two 30' 30K#'tow straps and shackles, leather and cold weather gloves, 2 gallons of water, 20 ton bottle jack, tire plug kit, bag of bungy cords and ratchet straps, roll of duct and electrical tape, full set of hand tools, ball pein and dead low hammers, 4 corner star lug wrench, 8x12 HD poly tarp, D-handle spade shovel, 2 small blankets and a medium size soft side tool bag of odds and ends. Am getting a 5 gal gas can to keep empty in the bed under my tonneau. You never know.
Of course on road trips I always carry my two carry pistols and 200 rounds plus my 10/22 and either my 30-06 or Mini 14 with appropriate amounts of ammo.
I carry a lot of crap. I figure better to have and not need than to need and not have. Whatever you do don't push the hours driving. Nothing wrong with pulling into a cheap motel even in the middle,of the day to get just 4 hours of sleep and a shower to help wake you up. You have two weeks so enjoy it. Do I sound like your dad yet?