2 weeks in Japan

I will be arriving Tokyo Narita on August 15, 2015 and depart Tokyo Narita on August 30, 2015. We will be 2 adults.

We will be staying in Tokyo 4 nights then hope to go to Kawazana for 3 nights then to Nanto for 3 nights then back to Tokyo for another 5 nights. Do you think we need to buy the JR pass? If not what is the alternative?

Is the JR pass valid on all Tokyo subway? Is the JR pass valid on all Japan railways?

We intend to do the Alpine route....can we use the JR pass to go there?

Thank you for your kind help.
Best Regards and have a good day!
Maithe.