Your questions have already been partially addressed by Gill, but you are correct that you currently cannot view the cumulative file size of collections or sort collections by file size. I will take your suggested changes to the team.
khernandezpardo, Gill's suggestion about sorting by quota used will help. Also, please make sure that you go to 'Trash,' select all files, and delete them forever. Files in 'Trash' still count against your storage limit.
In regards to the 119% issue, can you please provide a screenshot of where exactly you are seeing this?