I still don't know a way around it. But this happens when using other
numberformats, too.
I've used a custom format of:
mmmm dd, yyyy|dddd
(where | is the newline character--I use ctrl-j to enter it).
As soon as I shrink the columnwidth so that the text won't fit in the cell (when
measured if it were not wrapping), the cell displays ###'s.
I can fix the problem I see using this, but it doesn't look like it works for
your situation.
I can Format the cell
Rightclick|Format Cells|Alignment tab
Uncheck wrap text, check shrink to fit, and then recheck wrap text.
(and then adjust the rowheight manually)
When I tried the layout you want, the trailing dots were lost (shrink to fit
seems to cause the loss of the dots).
I don't have a suggestion for a workaround for you.