Typos, supplementary materials and essays.

Hi guys, 3 questions!

  1. I went back to my essay and found that I had a typo ('instsructors' instead of 'instructors'). How badly will that reflect on me?
  2. Also, how advisable is it to submit supplementary materials? I'm planning to send in an abstract from my research (for my major) and a writing sample (for my minor). They only come up to a page in total, but I heard that some schools aren't keen on accepting supplementary materials and it might just irritate the admissions office. (applying to cornell as a transfer)
  3. I wasn't satisfied with my essays. I lost my files a couple days before submission, and rewrote them at basically the last minute. Would it help if I added a couple paragraphs in my supplementary materials that better explain the stuff asked for in the essays, or would that just be too much and annoy the admissions community?