Highest melting point for the most durable plastic is 255°C (491°F) the problem is Elon Musk states the csr was NOT space hardened prior to decoupling. The roadster uses standard automobile plastics which melt at 100°C
the cockpit should literally be melting away into space
Not if it reaches an equilibrium at which it reradiates the heat nearly as fast as it absorbs it. Space is a vacuum and therefore does not exactly have a "temperature", that starts to depend on things like the proximity to the sun, the albedo, etc. I'd try to explain the difference between convective transfer, but 'm not really sure you'd understand... :-/
Space is extremely cold even though the sun is hot. This is because there is almost nothing in space. However, there is some heat in space because of very small amounts of atoms found in space. Space is only about 3 degrees Kelvin because of the small amounts of atoms. Therefore, the car would not melt.