Seeing as this LOR writer is imperative to your application, I will not suggest to find a different one. Instead, praise yourself more than you may even deem worthy. Go overboard in a reasonable way, and if your recommender does not agree they should change it. If you feel statistics are helpful, throw them in. Make up x percent and make up superlatives that you think are worthy of you, and when you send the draft over make sure to say that statistics and anecdotes are merely placeholders for the writers own views. Don't forget an introduction in an LOR is important. Teacher for x years, founder of this lab, etc.