Recent Backup update has corrupted my files and they can't sync due to lack of hard drive space

Recently updated my Dropbox App on Mac and had my computers 'Documents' folder synced to Dropbox, with certain folders as online-only so as to save space. The new update only allows for everything in the'Dropbox' folder to be selectively sync'd. This has resulted in files being kicked back onto my HD, but without enough space to store everything.

A few major problems that I don't know how to resolve:

• My Dropbox is stuck syncing files that read as 0kb after being pushed back onto the HD
• - i have tried many force quit operations, selective syncs, permissions, extensions
• A large proportion of my files that were backed up into the cloud are now reading as 0kb and are not available on my Dropbox, I think that Dropbox may have completely corrupted these files and i fear that i may not ever get them back again due to the way my dropbox was set up
• - i spoke to an advisor before realising they read as 0kb and they told me the update had changed the entire system to work differently
• I now am unable to sync any files that i save directly into any Dropbox folders, resulting in mobile app not showing me files, something i regularly use and think is so helpful is the seamlessness of being able to access files off of any device. 

In short, I am very worried and scared that I've lost a lot of files, I couldn't count how may, but looking through the finder, it seems like a majority. I'm a bit confused how this update has had such major oversight. For example, my HD space is 250GB but my dropbox plan is 2TB, with 1TB storage used; what did the engineers think would happen when dropbox spat all my files back onto my hard drive? My laptop is now full, but missing tonnes of files and unable to sync anything.. but stuck on "Updating 90,051 files".

Looking forward to anyone that can lend a hand! I've tried lots of different activity moniter / force quit / extension routes etc etc.