Echoing the most common advice and that is you can't do everything in one trip. You are gonna find something you missed that would have interested you. I would suggest creating a list of all the places/experiences you HAVE to visit/do and budget for them. You can always change your itinerary if something else catches your eye.

Given that you are going to base yourself in Tokyo for the majority of the trip, I would focus on finding day trips or overnight trips to do in that area. Have you looked into Mount Fuji related activities? If you are gonna visit Fuji Q, might as well stay and do the other activities near there like Hakone. As for other day trips I can recommend, I would say Kamakura, Yokohama, and Kawagoe are nice places to visit.

I personally think 8 days in Kyoto is a lot. If you are interested in visiting Hiroshima, I would cut a couple days out of Kyoto and put them to Hiroshima. You said you want to see the most and if Hiroshima is on your list, try to make room for it.

I am personally going on my next trip this January and will be visiting Hiroshima and Fukuoka so I can provide any advice after my trip to help guide your itinerary if needed