Anon, I hate to see your post going unanswered, but I think it's because we just don't know the answers to these questions. It would be great if someone who volunteered here was also an admissions officer at a program similar to the ones that people apply for here, so you could get good advice about what to include. Personally, I think a very brief summary of your academic achievements in your motivation letter sets the stage and isn't repetitive, as long as you keep it short.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.