Regarding the development of agreeableness/empathy: there are meditation techniques specifically intended to do this. (They are variously called "Metta", "Lojong", "Tonglen", or (yuck) "loving kindness meditation"; all of which are pretty similar.) These originate in Mahayana Buddhism, but don't have any specifically religious content. They are often taught in conjunction with mindfulness meditation.

I don't know whether there have been any serious studies on these methods, but anecdotally they are highly effective. They seem not only to develop empathy, but also personal happiness (although that is not a stated goal). Generally, the serious studies that have been done on different meditation techniques have found that they work as advertised...