I think it's a very strong letter. Succinct yet thorough. I'd be a little more specific about what kind of leadership roles you have. Are you supervising anyone? Managing a team? Leading community initiatives? Making presentations? It says you "led" the safety assay stuff in the first paragraph, but I think you could add a clarifying sentence after that. Aside from that, you don't seem to have explicitly answered the second question. I am assuming that's what the second paragraph is about, but I'd be really clear just to be sure they know you saw the second part of the prompt.