Computer Help and Support

(I don't use it, so I can't give detailed descriptions or directions.)

You should be able to download your photos and videos from iCloud to your computer, and then delete them from your iPad/iCloud to free up space (in theory).

Make sure to backup the files you retrieve from the cloud in multiple places just in case a drive or device fails. (You could even use a different free cloud drive service for backups from your computer.)

Perhaps you should ask in the Apple Users Group for advice on managing the storage space of iCloud - someone in there is more likely to be familiar with how it integrates with iPads and iPhones.