Month-long itinerary check!

Hi,

Firstly thank you for taking your time to help me vet me itinerary! It's our first time travelling to Japan so it gets pretty confusing for us, and we were simply contemplating a few questions, but firstly here's out itinerary so far!

Day1(29th May, Fri): Arrival in Narita at 7pm, off to Tokyo!
Day 2: Tokyo
Day 3: Tokyo
Day 4: Tokyo
Day 5: Tokyo - Day trip to Nagona, visit Matsumoto whilst returning
Day 6: Tokyo - Day trip to Nikko
Day 7: Tokyo - Day trip to Kamakura
Day 8: Tokyo
Day 9: Nagoya
Day 10: Nagoya
Day 11: Nagoya - Day trip to Magome & Tsumago
Day 12: Takayama
Day 13: Takayama - Day trip to Shirakawa-go
Day 14: Kyoto
Day 15: Kyoto
Day 16: Kyoto
Day 17: Kyoto
Day 18: Kyoto - Day trip to Tottori Sand Dunes
Day 19: Kyoto - Day trip to Nara
Day 20: Hiroshima - Leave big luggage overnight in Kyoto
Day 21: Hiroshima - Explore Okunoshima Island and back to Kyoto
Day 22: Kyoto
Day 23: ??
Day 24: ??
Day 25 ??
Day 26: Osaka
Day 27: Osaka
Day 28 (25th June, Thur): Osaka - Fly back to country at noon!

So thats the rough itinerary for now! So the few qns:
1. Is it worth getting the JRpass for the trip? either 21days or a smaller amount for the travelling parts.
2. Is it too much travelling packed together? (the day trips)
3. Could someone help me fill in the blanks for 3 days.. I can't think of much to do anymore!

The flights are pretty much confirmed for us so we must end in Osaka! Also, we would be having quite a lot of luggage so I would think it would be better to stay in a central location and go on day trips from there on out! Please advice me if I'm wrong!

Thank you for reading and have a pleasant day! :D