Jim Laumann wrote:

-snip-
The got'cha being that if I crack the broken section while drilling or
tightening the fastener, its broke for good. Is there any adhesive
that I could use for such a repair?

I used "landscape block adhesive?" to glue the top row of blocks on my
2-foot retaining wall. It has held for 3 NY winters with people
walking all over them, so I'm a believer in that stuff.

I think I've seen an 'exterior grade' construction adhesive, too.
Read some labels.

Jim