10 days in Japan

Hi JR pass, I'm going for the first time to visit Japan. I will arrive to Tokyo May 3 (Narita) and departure from Tokyo (Haneda) 13 May. The plan visits I have the following:
May 3-6 Tokyo
May 6-10 stay in Kyoto with trips to Osaka and Nara
May 10 trip to Hiroshima with a break half day trip to Hinami
May 12 return to Tokyo
May 13 departure from Tokyo.
Im going to buy Pasmo or Suica IC card for staying in Tokyo. . JR Pass I will activate at 6-th May at trip to Kyoto. What do you think about buying a JR Pass? Is it worth? Can I go twice Bullet the same day. : Kyoto -Hinami than 1/2 day break w Hinami and Hinami-Hiroshima ? What will be with seat reservation ? Where to do a seat reservation and where buy 2x ticket for Kyoto-Hinami, Hinami-Hiroshima

thank fo answer