The essay is written from your point of view of yourself based on the scenarios provided. The discussion presented is what you believe are your best traits that the reviewer should take notice of. You totally missed out on the correct point of view consideration for this essay which is:
How would your family, friends, and/or members of your community describe you?
This means you have to disengage yourself from the writing. Use the third person point of view. If possible ask these people to write a short character description of who you are and what they believe are your best traits as a son, friend, and community member. Do not observe yourself and write about yourself. By finding out what these people like the most about you and how they describe you, a character based personification of who you are can be provided through what you are most proud of.
These common app prompts are meant to get to know the student beyond grades and academic accomplishments. So it would be best not to mention the grades because the transcript of grades should represent that aspect of your academic strengths and weaknesses. However, if your grades as so horrible that you feel there is a valid explanation for it, then you can try to explain that through the open topic prompt. Although, I would not advise it, again, because their main consideration for the grades will be the records you submit rather than the explanation you will provide.