Advice on itenary

Hello
This summer we will travel with 5 adults to Japan. Our itenary will be like:
Day1-3 Tokyo
Day 4 train to Kyoto
Day 5-7 Kyoto
Day 8 train to Hiroshima
Day 9 Hiroshima
Day 10 train to Osaka
Day 11-15 around Osaka (rental car)
Day 16 Kobe
Day 17 train to Hakone
Day 18 train to Tokyo
Day 19 depart

I was planning to take the 5day Kansai-Hiroshima pass and separate tickets to and from Tokyo.

Would that be the most economical way if train travelling?
Best to buy tickets before hand?
When to make reservations?

Looking forwarden to your advies!