<snip>
> Does anyone know of a way I could ground the *inside* of the steering
> shaft? The rack end is sealed and lubricated on the inside, right? So
> the only way/place I could do it would be the exposed end at the
> wheel, or where the ignition locks the shaft, right?

I found a way to do it, for anyone else that may have the same issue.
Basically, I used an "unused" spot on the cable reel assembly to run
the ground through. I am a bit concerned, however, since it appears
that unused spot was meant to isolate the SRS signals from the cruise
and horn circuits. So far, the air bag hasn't accidentally deployed,
though!

And now, at least the horn works reliably. Hope this information helps
someone else out!