Hi Josefin,
Sorry for the late response, its been a tad busy over here, however I've not forgotten your previous questions.
You would be making savings with both the 7 day JR Pass and 14 day JR Pass. However I would recommend going for the 7 day JR Pass and plan in such a way to you can cover your return Tokyo - Kyoto with it and at least your visit to Nikko and then use local tickets for the rest. This is probably the most cost efficient way of travel.
If you want more freedom, flexibility and more JR go for the 14 day JR Pass.
For reference a 7 day JR Pass is 28,300yen and 14 days 45,100yen.
Also I read that you plan to visit Fuji, depending on the area an additional fee may be required some some routes are partly traveled on private railway companies. For instance Tokyo - Kawachiko is covered up to Otsuki stationed (3,060 without the JR Pass) and requires an additional fare from there of 1,110yen even with the JR Pass. However there are still pretty good savings to be made!
Again sorry for the late replay and all the best!
Daniel