Try some fingernail polish remover.
superglue
that's a way to remove blisters, once you get superglue on it, and peel it off, your blister is gone
I wouldn't, superglue or CA glue when cured becomes very brittle, its like hard plastic, when your stained glass project flexes, (and it will) the the CA glue will crack and fail.
Super glue, or take it to a glass-blower and have him 'weld' it with glass.
Cut it out then put a skim coat of mud over it.
It can be heated and change appearance, can be painted or stained, can be hardened.
Get superglue debonder.
Best practices dictate that you take your gemstone to a local jeweler who may be able to help you remove the superglue.
Diamond can cut glass, but so also can Emeralds and Topaz, Quartz, Tungsten and hardened Steel.
It can be heated and change appearance, can be painted or stained, can be hardened.
Not to sure how to remove it but to prevent it add a pinch of dried rice in it
The best way is to soak it in hot soapy water.