Hi Vikky
It is hard for me to say if the starting up a company and runing a company is leadership?. I believe it is more of entrprnshp. And it is of same difficulty to define leadrship. A leader is someone who is of good charector, motivates people and lays a path to be followed, while taking responsibilities is any effect in this path and correct it. Thats my definition. Check it out if there were any situation during the running of the firm, where you had to stand in the forefront, to set the rules, to guide your subordinates....
When writing essays, NEVER forget to give evidence. There is no point if someone writes, I posses execellent communication and leadership skills, if he does not provide any evidence. It is a MUST. Your exprnce with the NGO will act on ur favour. Your novel writing shows you have interest apart from just business (which again will differentiate from the 2445 application that these school recieve).
All in all, be true in your words, be self. Trust me, when I wrote my essays, I sort of discovered myself. And what really interests me, which school suits me etc...It really, really really re-defined my ultimates goals.
The factors will have good impact on your application, but I would never underestimate the others who would be applying. Not to discourage you, but I know a person (a very close frnd) with a 700 gmat, a business deveopment manager in china (not a chinese), who cam here to start a business from stratch and now the turn over is quite good, who was rejected by Stanford. You would never know till you apply. Give a lot of time to the essays (but gmat is prime to - it the key to the first door). Proof read your essays with your best frnds and also take a 3rd party opinion. See if their opinions match. Then revise the essays, before your final submission. Wish you good luck.
Regards