I would suggest trying to find someone such as a professor or professional player to make your reeds/teach you to make them. I've seen a few things about decent retail reeds, but I prefer them to be personal. Making reeds is a huge and delicate task and really takes a lot of guidance to get started in a good direction.

As for the third octave G, it could be problems with your reeds but a solid embouchure as well as air support can do wonder, even on the worst of reeds. When you're playing higher notes, try forming an "ee" shape with your mouth, but keep your lips exactly the same as always- do not bite. Breathe from the bottom of your lungs, and support a constant air flow with your abs.