Is this something we have to complete in one sitting or is it legal to stop gameplay and pause run time so we can sleep and then wake up later and continue?

You can sleep, eat, go take a shit, whatever, but you have to leave the timer running for the entire duration of the run, no matter what you yourself are doing. It says it in the rules, which you should read very carefully if you plan on running 100%.

Gotcha.

If you have a setup in the bathroom, you don't even have to stop playing to take that shit. Just a little tip from me to you!