yes, you definitely run the risk of melting the bushing. Do it at lower heat, shorter intervals. You probably wont be able to get the bolt red hot, just get it to the point where it is smoking out both ends of the bushing. wait a few mins, then I guess you could try and punch the bolt out, or try and get a vice grips on the end, and twist it loose.

However, I dont foresee you being able to do anything but drill it out at this point.