OK, so, how does this woman adequately care for her kids, without fear?

I think, using the idea of disunity at the beginning of the movie, moving toward unity at the end, that her motherly instincts kick in as a result of the fact that her lack of fear put her children in danger. Something more primal than the amygdalae kicks in that creates a desire for natural levels of fear. And she finds a way to heal the damage, but because she's never dealt with fear before, she is temporarily paralyzed by these new and overwhelming emotions. She has to learn courage after she experiences fear and, again for the sake of her children, fights against a desire to become a recluse.

You could do a sci fi-drama angle. Say, a person crippled by multiple phobias who agrees to take an experimental drug to curb the fear response. And it works. In fact, not only does it rid him of all his phobias, he has no fear at all. At first, it's great. No self-doubt, no trepidation, no hesitation. He can do all the things he's always been too afraid to try - demand a promotion, be the life of the party, sweep women off their feet, run off muggers.

Then the downsides start coming out: He takes crazy risks, because he can't judge danger anymore. His life spins out of control because he has no restraint. The doctors want to take him off the drug - the experiment's a failure - but he can't stand to go back to being that sad, terrified, lonely person imprisoned by his own phobias again. What's he going to do?

Sort of a "Flowers for Algernon" take, but with fear instead of intelligence.

Patrick Sweeney
I Blame Ninjas

@Firefly Games: I like your take, and could especially see this played out in a crumbling of personal relationships, like the protagonist's marriage. When I read about the real SM being on the receiving end of a domestic violence incident, my first thought was a guy getting so angry at her for not feeling fear that he starts knocking her around in a dramatically escalating scene to goad her into feeling fear - sort of like the pivotal test that Leonard's wife put him through in Memento over whether or not he really had lost his short term memory.