Hey there @Malthasian, thanks for reaching out!
Since this is a rather large folder, I might suggest adding the content to Dropbox in batches.
If you create a new empty folder (with the parent name) in the Dropbox folder, you can copy over a few subfolders at a time (depending on how much space you have free).
Once you've added one or a few subfolders, you'd then need to allow the app to sync and upload the files to your account.
When the app is showing "up to date", you can then use selective sync to remove the folders locally from your computer to free up the space.
You can then repeat the process and add a few more subfolders. Would this do the trick for you?
Looking forward to hearing from you!