So, given that my #1 plug is totally trashed (see picture at http://
xochi.com/vanagon/Plug1.jpg ), i'm guessing that a valve broke in the
# cylinder?   Are there other possible causes of this kind of
damage?   The wasserboxer is a non-interference engine, right?

Seems to me that with a 150k mile engine with low oil pressure, after
this amount of metal has been running around inside, it's not worth
trying to repair.

Which sucks.  On the other hand, the long-term plan has always been
to get a new engine in this beast.   So, in a way this is a good
thing, as now it's "new engine shopping time!"