Just to clarify:
(1) If a block is attacked and defeated, does it exert a FoF until it retreats in the owning player's withdrawal phase?
(2) Can enemy blocks pinned in the defeatted block's field of fire march move after the successful attack, considering that the successfully attacking block(s) sit athwart its position?
(2) No. They cannot march.
There is a note on this at the end of the first column on page 11.