2 and 3. The origin is from the dorsomedial edge of the coracoid at its extreme proximal end, and to a slight extent from the adjacent portion of the manubrium.
"Thoracic and Coracoid Arteries In Two Families of Birds, Columbidae and Hirundinidae"
Marion Anne Jenkinson
See that the biceps are in their grooves, and ribs on spine are true at manubrium and spine, and that neck is true on first dorsal.
"Philosophy of Osteopathy"
Andrew T. Still
We recollect that, in its inferior part, it is divided into two bundles, one of which arises from the manubrium of the sternum, and the other from the inner third of the clavicle, whence the denominations of the sternal portion and clavicular portion.
"Artistic Anatomy of Animals"
Édouard Cuyer