Hi,
Epoxies are thermoharders, which means that, once set (from mixing 2 base components) , you cannot melt them any more (unlike thermoplast e.g. poly ethylene, PVC, Polypropylene), see also
So meltingan epoxy potted circuit, by applying heat is impossible (same story for other well known thermoharders loike bakelite, nitrilrubbers etc.).You cannot melt car tyres.
Also Epoxies are chemically very inert (so dissolving it with nasty chemicals is not only very dangerous but would dissolve the components you are looking at.
Judiciously softening epoxy potted circuits by heat can be done (see photo of a "depotted"Motorcycle / aeroplane voltage regulator),but you have to control the temperature much better than you did (your temperature steps were too coarse) and it takes a lot of "Elbow Grease".
