...in the "temporary directory" (tagged with different datetimes). This has taken up extra disk space, is this necessary?

If you have interrupted any of the backup jobs, the file tagged with the datetime of the corresponding backup job will be renamed to its original filename just before it is uploaded. This is necessary as we need to ensure that the snapshot of different dates would not overwrite each other.

If a backup job is still running, just let it runs to completion. If backup has been stopped already, just remove all files tagged with the corresponding datetime in the “temporary directory” and try to perform a full database backup again.