Personally, I skip the house work.

Much to the irritation of my housemate.

Seriously, though, while I'm not the one to ask about time management, you might want to prioritize things, and concentrate on the highest priority items (which might change from day to day as tasks formerly on the backburner come forward). Maybe some of the short stories move to a lower priority during this time.

Also, remember, Prep is a 15 minute exercise (minimum). Even if you add time to read the instructions and get all your files or webpages or whatever open, it's 20 minutes. Consider scheduling that like you would a doctor's appointment or a dinner out. "I will drop what I'm doing at 7:10 and work until 7:30" or whatever.

In the end, if you can't find the time to do Prep, you might need to consider that you won't have the time to do NaNo next month. 1700 words takes more than 20 minutes for most people. That's okay; you can plan on a shorter story that takes less time to write, or decide for yourself to stretch it out.