I personally love Kanazawa and I enjoyed Fukuoka. Whether you need to visit them really depends on your interests and your boyfriend's interests.
Personally, I don't think Osaka needs 4 nights. I can see needing a night before USJ and a night before you fly home, but otherwise I would just stay more nights in Kyoto. I enjoyed USJ as well as Himeji, but I find Osaka itself sort of boring outside of shopping and visiting my friend and I can do both those things and stay in Kyoto. But again, it really depends on you and your interest.
I confess, I am a bit confused by your choice of wording. I'm assuming since you said your total was 23 days and you only listed 16 nights at various locations that you're not counting travel days in your total for various nights at various locations.
For USJ, Tokyo Disney and Fuji Q Highland (especially the former 2) make sure to check the crowd calendars and try to pick week days that are not holidays. I think Fuji Q is not as crowded as USJ or TDR, so just avoid week ends? I've only been to USJ and TDR, I'm waiting until my child makes more heightlines to visit Fuji Q and Nagashima Spa Land.
Aso is not all that close to Fukuoka. It's also a location that is best accessed via rental car. Aso Station is about 2 hours via bus from Kumamoto and then another 30-40 minutes trip from Aso Station on a bus that runs every 1-2 hours. Outside of the train to Kumamoto from Fukuoka, none of the trip to Aso is covered by a JR pass. The JR line between Kumamoto and Aso Station was heavily damaged in the 2016 quake (See here: https://www.japan-guide.com/e/e4551.html
) With a rental car Aso is about 2 hours and 21 minutes from Fukuoka proper according to Google Maps or 1 hour and 30 minutes from Kumamoto, starting from Kumamoto Airport drops it down to 1 hour. (Though I hear Google Maps driving estimates are off.)
If there is no specific order you need to do things post your Tokyo nights, have you thought about flying from Tokyo to Kumamoto and then working your way back to Osaka/Kyoto? If you don't rent a car Kumamoto airport is a stop along the bus route to Aso.
If you fly, I would probably not pay for a full JR Pass for 21 days and would see if paying out of pocket for some tickets and getting a regional pass or passes might make more sense.
I hope this helps!