Disk space not freed after deleting files, unable to save things, unable to delete things, unable to update things
If you've "upgraded" to the Photo app from iPhoto or Aperture, your photos would have been imported as hard links. Basically this means that each photo is represented by both programmes and deleting from just one has no effect on the actual photo file. You'd need to delete from both.

Check to see if you have another album in your Pictures folder (or other folder if you manually placed it somewhere else) and delete the photos (hard links) there.