I walk that line very well. Dark humor helps me cope, and when combined with self-awareness, at least in my experience, allows me to keep my empathy/sympathy muscles well maintained. That is to say, making the dark joke with the awareness of its darkness allows me to continue to feel empathy. I dunno if that makes sense, but that's how it works in my head and I continue to have an incredible sense of empathy, sometimes even to my detriment.