Eliminating or mending breakage when working with jeweler's wax
As I recall there are grades of microcrystalline wax available in different hardnesses and melting temperatures, so do try others.

I have always used a moldable base to support detailed work. Pitch mixed with Plaster of Paris is the old reliable method. This can be softened with a propane torch, the work pressed in, and upon cooling - you have firm support and if you slip, the pitch won't damage your tools. It's also black which provides strong visual contrast so you can see what you're cutting. If need be you can cut away the pitch in areas where it's in the way. Use chisels for this, a rotary burr will gum up unless you're using a coarse tooth at low speed.

Bees wax is used similarly either pure or mixed with stiffeners like plaster or diatomaceous earth. Plasticine works on some jobs, but vibrations from rotary tools tends to loosen the fit more than beeswax or pitch.

Pitch can be removed with turpentine or mineral oil which won't affect most waxes.

See "The Complete Metalsmith - An Illustrated Handbook" by Tim McCreight, Davis Publications, 1982