1) Etheric fields determine sexual compatibility; astral bodies determine emotional compatibility. That's why those two are not necessarily found in the same person!

2) Iron is a good etheric conductor, meaning that it doesn't store etheric energy -- the energy flows out through it. The patina that bulds up on a good cast iron pan is another matter, and yes, it can hold etheric charges.

3) We don't know. Seriously, we don't know.