Sorry for disappearing for two months.

After switching Paravirtualization Interface to KVM, Excel4 went 15 days without crashing with the same routine of letting it sit idle and playing with the arrow keys and shift for selection.
A real usage test-drive has not yet happened as I was waiting for him to be done with taxes and such important stuff before potentially disrupting his workflow. I'll probably set him up next week.

Hopefully two weeks later I can report it went fine.