Hello Agnesylui,
Below is a quick list of the most expansive routes in your itinerary. Note that the Shinkansen bullet train station for Fukuoka is called Hakata.
Osaka - Hakata ¥ 15,000
Hakata - Osaka ¥ 15,000
Osaka - Tokyo ¥ 14,140
For a total of ¥ 44,140, the price of a 14 day JR Pass is ¥ 46,390. So the difference is quite small, add in travel to Kobe/Kyoto/Nara and local travel on the JR lines and the JR Pass will be a good option. In this case it won't give you huge savings but still significant savings. Also the JR Pass is your single ticket for all of Japan, making it much more convenient that buying train tickets each time you travel.
Hope this helps,
Daniel