Regarding the different statements of usage on your iCloud+ account, if using your iPhone you navigate:
Settings > Apple ID > [Your Name] > iCloud > Manage Storage > Family Usage
you will see the amount of your shared space each separate family member is using. This can be seen also on a Mac, and probably iCloud for Windows. The amount of space used by each member will not be the same because everyone uses iCloud differently and for their own purpose. Or are you saying that you are getting different numbers at the same screen on different devices?
If you have reached the ceiling of your 200GB plan it might be time to consider moving to the next plan up - see Upgrade to iCloud+ - rather than desperately try to reduce your iCloud+ space in use. The difference in the monthly cost of your current plan will be a modest investment for your family's needs.
Despite your best efforts to reduce the data using your iCloud space it's rather like trying to use a broom to sweep the waves back into the ocean. Your daily apps alone such as Messages, Mail, and Photos for example are all great consumers of space.
For the immediate future, consider all the tips in Manage your iCloud storage which is also linked above, though it seems you have already acted on some of these suggestions.
