Cannot create bootable USB with Boot Camp, "there is not enough space available on the disk"
The error message is not warning of insufficient space on your internal disk, but rather that of your external USB drive. Make sure there is sufficient space on your external drive and that it is of a sufficient size (at least 16 GB, possibly more depending on the Windows installer you are using).

The system log snippet provided is not relevant to Boot Camp but rather that of Microsoft AU, the updater for Microsoft Office.