Maybe you have done this but just in case - you want to cut the dropout in 1/2 between the chain and seat stays so that there is a piece of the dropout hooked to each stay. Grab the dropout with some vice grips and position the frame so the dropout is low and then heat the dropout a good bit so the brass will flow out of the stay and onto the dropout. GENTLY wiggle the dropout with the vice grips. If you are heavy handed you'll break the end of the stay off. Wiggle it gently and you'll feel when the braze is all soft and the dropout part will slip right out.

By cutting the drop you make it so you need much less heat. If you were already doing this I apologize.

dave