[throwitawayday]

On 3), the giant fiber is fast but not faster than other descending fibers. If anything, it is more reliable in its ability to signal.

See: https://www.nature.com/neuro/journal/v17/n7/full/nn.3741.htm...

Short abstract snippet (the "parallel circuits" are other, non-giant descending neurons that also trigger the escape behavior upon a looming stimulus):

"Intracellular recording of the descending giant fiber (GF) interneuron during head-fixed escape revealed that GF spike timing relative to parallel circuits for escape actions determined which of the two behavioral responses was elicited. The process was well described by a simple model in which the GF circuit has a higher activation threshold than the parallel circuits, but can override ongoing behavior to force a short takeoff. Our findings suggest a neural mechanism for action selection in which relative activation timing of parallel circuits creates the appropriate motor output."