Fortunately I had a 9 TB datastore that was currently unused that I could put in the Scale-out repository and could evacuate the offending datastore with space I still had available. So that's what I did. 49 hours later and that job is still running. I guess that's what you get when you are on 2 trunked 1 Gb network connections.
After I had the first job fail because the files were on the repository we were evacuating, I disabled the rest of the jobs. I was hoping that would speed things up. I guess this is the sped up time! On top of that, this is my Sun-Thu week so I'm supposed to be off for the weekend starting tomorrow. If this job doesn't finish before I go home tonight, I think I'll turn the backups back on tomorrow morning. Then Saturday I'll fix my over-provisioned datastore and evacuate the repository I "borrowed". Hopefully when I come in Monday, all will be back to normal and I can enable all the backups again. I'm not leaving the 9 TB repository in the Scale-out repository because I'm retiring that hardware. We've been using it since 2011 - it's time! We're getting a Synology NAS with 10 Gb ports. Fortunately I still have available 10 Gb ports in my switch.