Borax flux is NOT the same kind as the acid flux used for stained glass.
For earwires you probably need 20 or 22 guage wire, for head pins for small hole gemstone beads you could use 24 or thinner.
Even with a torch, making clean looking balls at the end of a wire is not easy. Rings & THings co-owner, Dee Mueller, used to make them for her line of fine craft jewelry. She says they were never very uniform looking. Even with flux they tended to be pitted and rough. The pressure of the torch flame blows the 'blob' at the end of the wire away from you so it isn't quite centered. Her best ones were made with a small oxy/propane torch and the wire hanging down from a third hand.
Hand made ear wires on turquoise and silver earrings we used to sell also had a problem with pits on the teardrop balled end.
If anyone reading this has better suggestions or tricks we'd all like to hear them!