Which JR Pass should I buy?

We (3 of us) will be in Japan for 8 days, here is our itinerary:
Day 1 : Travelling from Kansai Airport to Kyoto (should we buy a separate train tickets for this or perhaps take shuttle taxi service such as Yasaka Shuttle?)
Day 2 ,3 &4 : Sightseeing in Kyoto ( Can JR Pass be used for sightseeing in Kyoto?)
Day 5: Travel from Kyoto to Higashi Hiroshima
Day 6 & 7: Daily travel to Hiroshima from Higashi Hiroshima including Miyajima
Day 8: Travel from Higashi Hiroshima to Osaka, then to Kansai Airport for midnight flight

My questions:
Is it worth buying 7 day JR West Pass?
If yes, should we activate this on Day 2?
Where can we leave our luggage while sightseeing in Osaka on Day 8?

Thank you so much for your help.