And the rest of the progress was deleting all the snapshots. Worked great after that.

actually just made some progress after I typed this. The wizard was trying to read file sizes of mounted DVD images in the virtual DVD drive of offline VMs. I deleted the DVD drive from those machines and the fuse mount of the ESXi storage proceeded.

edit: and got one down successfully. So far it appears the free license of ESXi is no hindrance.