Hi,
You don't give your full itinerary, and if you are going round trip Tokyo-Kyoto-Tokyo it is relatively easy to make a 7 day pass worth it. But while going all the way up to Sapporo by rail would make a pass pay off, given your limited time it would kill 2 whole days of your trip with about 10-12 hours on the train each way. It would be far wiser to take a discount air ticket such as on Jet Star or Peach, for less than $50 each way. A pass would only make sense if you were to stop somewhere along the way and take a couple of days to get up there.
Presumably you are going for the Snow Festival, which for 2016 is Feb 5-11. Needless to say, it will be quite frigid during that time in Hokkaido. But there is also some killer skiing there if you are inclined.
If you want to see rail schedules, see Hyperdia.
The pass cannot be used on city subways, buses, etc. Most cities have a day pass for each though if you travel extensively.
Best of luck!