Ok, I was able to delete the container after restarting my computer (I just lost all the work I did this weekend), but it didn’t reclaim the hard drive space. To be clear, I had 70 GB of free hard drive space that is now being held hostage by Docker.
I followed these instructions which reduced it by about 25 GB, but that’s a far cry from the 70 GB I had moments before the “commit” command.