If you want to know if a pass will be a cost win you'll need to price out your individual trips and compare to the cost of the pass. You can do that here.

Pass won't be of much use within Tokyo. Some but not much. There are _many_ trains and busses you would want to use while in Tokyo that are not covered.

Yokohama to Niseko is a _long_ train ride. You might be better off flying.