Did a bit to try to answer your first question. I put a brand new ce2 under the microscope. I then put it under alcohol and rubbed the surfaces clean with a wooden stick while still under the microscope. Finally, I applied a hot soldering iron brimming with lead solder to the joints to test the approximate melting point. Please understand that my conclusions are necessarily unconfirmed guesswork.
Traces of what appears to be resin appear mostly in crevices on and around the two solder joints. There is also a bit of resin in the metal cup near that solder joint where solder or resin may have splashed or otherwise been applied away from the actual joint. The resin does not come off easily from soaking in alcohol, but does comes off with vigorous rubbing by a soft material while wet with alcohol.
Traces of a white substance appear to stain or bind all along the surface of the metal peg. These appear similar to those that appear after washing solder and resin (e.g. with alcohol) from a typical circuit board. Whatever this substance is, it may come from the resin or some other kind of coating.
Molten lead solder applied to the joint floats around the joint for a few seconds, indicating that the native solder has a higher melting point, which is likely with unleaded solder. While melted, the two solders don't mix well. After cooling, distinct strata appear in the hardened solder blob, which is consistent with two disparate materials hardening at different temperatures or times.
Other debris appear in the fresh (still dry) carto, consisting primarily of many small threads, and a much smaller quantity of black specks. The way they stick suggests that some liquid medium was involved in their dispersal or aided in their sticking.
It's always scary putting anything under a microscope. This was no exception. It might be a good idea to give these cartos a long soak in alcohol, a quick boil, and a long rinse. If you have a paint brush and can open them, it might pay to rub both solder joints well while soaked with alcohol. It makes me wonder what's in my other cartos and attys.