Restore from iCloud Backup lost ALL my photos — Ideas?
I recommend restoring those backups. 
iCloud Backups are compressed to save memory. Just because they show lesser GB than the full amount of your photos and videos may have, doesnt mean that they arent there. Also backups are done over time, so the photos and videos are also saved over time, never all at once.

I would restore from a backup and see what you have. Also when the latest backup was installed, did you have iCloud library turned on in iCloud settings? If so did you have optimize storage turned on? You'll want that off if your iPhone has enough storage for your photos.

And lastly make sure you go to www.iCloud.com since all photos that iCloud can send to your iPhone will come directly from there as well as your backup. See if you can verify that before giving up on the backups.