Can you show us the "setting" - meaning the ring with the empty hole?
Since I've done both glass and metal smithing, I'm thinking you may be headed for disaster if you try and place a hot glob of glass into a 14k setting!
So think through all possibilities before you give it a try, and maybe there's a better way...
Have you thought about precisely measuring the "hole", then trying to make a small bead or cab that will fit down snuggly into the hole?