1. Mapping to templates starts with the initial state of a symbol, similar to dragging it from the palette to the drawing area. There is no way to keep existing properties but you can restore the text by adding an appropriate mapping to the Label Text to your configuration.
2. There is no way to copy custom property settings from one diagram to another but you can use an existing one as "template". For this, simply save the existing with a new name and delete its nodes and connections.