How should this Bendix course deviation indicator from the '50s be read?
This is an early version of an HSI.  The heading (depicted by the airplane) is either set manually, or it's slaved to a remote compass.

Responding to the question as numbered:


Depicts wind correction angle when tracking a course.
To/From flag
Glide slope reference (too low)
Push to test the warning light.  Also push to illuminate while turning to adjust brightness.  This may light without a valid heading source from a remote compass/flux valve.  It may also be to indicate failure of an internal gyro if so equipped for heading source.
Depicts aircraft the heading