Hey hey! First time commenter so go easy on me.

I personally use Symbols for Sketch if you don't mind getting a little dirty with the command line.

All of the nitty gritty is handled through sketch, you can name your artboards the unicode required as well as a class name. That will stop your pesky glyphs moving about. Then hammer in a command and pow! It's exported in all the flavours you need! Give it a try and holla at me if you need help getting to grips with the nitty gritty.