Can I melt cured silicone down and reuse it

No. Silicone rubber is a thermoset and has no melting point. During curing, cross links form between the polymer chains, creating a three dimensional network in which every molecule is chemically bound to the next. That network cannot be turned liquid again.

Heat silicone rubber far enough and it degrades rather than melts. You get no usable material back, only degradation products and fumes. An oven, a heat gun or a gas torch achieves nothing.

This is the essential difference with a thermoplastic such as PET, HDPE or casting wax. Those materials do melt and are therefore reformable, which is exactly why they fit into regular plastics recycling and silicone does not.

What does work is mechanical reuse. Cut or grind cured material into chunks and cast them into a new block mould as filler. On an industrial scale there is also chemical recycling, where catalysts break the network down into shorter chains that serve as raw material again, but those plants only run on clean, separately collected production streams.

Read more: reusing cured silicone in a new mould