By all means, remove the glass cab before you apply the torch to the
silver. By the time you get the silver hot enough to melt the solder
(1300 or so for easy solder) you will probably have heated the glass
into the range where it must be annealed as it cools down. Without
annealing, glass cracks from internal stress.
If you mounted the glass cab with a bezel, it should be an easy task
to slip a thin blade between the glass and the bezel and straighten
the bezel back to its original upright position and remove the
stone. If you mounted the glass with epoxy or E6000 adhesive, gentle
heat (I use a hair dryer) applied to the silver may soften the
adhesive enough to get the glass off.
Is the cuff constructed so that you could simply saw off a bit from
each end and finish?
Lots of luck.,
Craftsmith Studios, Santa Fe