Why are the responses in the fight-or-flight system so widespread and lasting in the body, but activation of the parasympathetic nervous system is discrete in comparison?

Because responses to the fight or flight system occur through adrenaline, while adrenaline production is not stimulated in the activation of the parasympathetic nervous system.

Explanation:

The escape or fight system is activated when we are in a situation of extreme danger or stress and our body wants to get away from that danger as soon as possible. To get you out of danger quickly, the escape or fight system stimulates the production of adrenaline which allows responses to this system to last for a considerable time in the body.

On the other hand, the parasympathetic nervous system is not intended to make you move quickly away from danger, or face you for protection. On the contrary, this system has the function of making you calm down and for this reason, the production of adrenaline is not stimulated here, so the activation of this system is made discreet and delicate.

b.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."