#2
The components are as follows:

* A dual-ganged potentiometer (top = 1 MOhms, bottom = 500 kOhms)

Basically two potentiomenters (one 1 MOhm, the other 500 kOhms) controlled by one knob (for lack of a better word)
#4
not a clue tbh, try rapidonline.com or rswww.com. Rapid are cheaper, but RS stock more speciality componants.