Given your particular situation, leaving blank seems like a reasonable course of action --
It sounds like you went through He!! but were one of the few who made it out stronger. You were forged, not broken. If you haven't sought counseling to help you digest and make sense of things, it might be a good idea now. I'm not suggesting you "need" it in the conventional sense, but rather that it might help you come to terms with it in a way that makes it easier to explain succinctly and cogently with the level of emotion you choose to bring to the table. It would be easy to come off as angry, bitter, victimized, callous, helpless, martyr, hero-complex, enmeshed -- any number of things reflecting any number of conflicting feelings you have every right to feel. I'm suggesting counseling more as a pro-active 'sort it out in hindsight' thing --
Best of luck to you --