Hi there,
I've made a little list of normal ticket prices below to see if a JR Pass would be helpful to you.
Haneda Airport - Tokyo ¥ 650
Tokyo - Disneyland/sea ¥ 220
Disneyland/sea - Otsuki (for Kawaguchiko) ¥ 2,940
Otsuki - Kyoto ¥ 15,360
Kyoto - Shin-Osaka ¥ 2,810 for the Bullet train, there's also a local service for ¥ 560 yen
Osaka - Nagoya ¥ 6,560
For a total of ¥ 28,540 the 7 day JR Pass is ¥ 29,110. With travel in Tokyo you would either break even or make small savings. Since there is little to no difference in price, you could consider the JR Pass for the convenience it offers. As you just need one ticket for most of your travel and don't have to buy separate ticket each time you travel.
Also, I am sure you noticed that I put in Otsuki below instead of Kawaguchiko. This is because when you travel to Kawaguchiko there is a transfer between trains (and train companies) at Otsuki station. The JR Pass covers the route Tokyo - Kawaguchiko and from there the last part is travelled using the Fujikyu line (~1,150yen). Which is not included in the JR Pass.
The best way to travel from Kawaguchiko - Kyoto with the JR Pass is the travel back to Otsuki and from there travel on.
Hope this helps!
Daniel