Any 7 nights in a row are a week. There are no set weeks with DVC like a traditional timeshare. So you could even do Mon-Mon, Tues-Tues, ect. There are also no discounts for booking a week. If you do not have the week listed on your chart, just add the 5 week nights to the two weekend nights for your week total.
Only if you plan to check out and leave on Sunday. If you plan to spend Sunday night, you would need to have points for that night. The easiest way to think of it is think what NIGHTS you will need to sleep in the room til the next morning!
But, if you need to have a room past 11 am you would need to book an extra night. We always leave on the last flight of a day (8pm ish) and check out of our room about 10:30 am to 11 am. We then use the showers in the fitness center if we need to freshen up before we head to the airport. Bell services will store your luggage after you leave the room, they can also store luggage if you are arriving before your room is ready. We have used this service for almost every trip we have ever taken and it works well for us. Check in for DVC rooms is 4 pm and check out is by 11 am. No late checkouts can be permited with DVC as the rooms require more cleaning than a typical hotel room, but there are occasions where a room will be available prior to 4pm, but do not count on that.
Hope that helps some!