A year ago I made a round trip from CA to IL to purchase my my divorce house, and then the one-way moving trip in August. Almost all of it was on Interstates.
Driving solo with my little dog, I found www.interstaterestareas.com
very useful for finding places to stop, stretch, get the lil guy out, nap etc.
Every evening or morning before departure, I checked this website for the mileposts of any rest areas on that day's leg and wrote them on a note card.
The web site even notes which areas are closed, and there are also comments from users.
Then, when Reggie got restless or I got hungry or drowsy, it was easy to tell how far to the next rest area.