Excellent points, but frankly your letter will get trashed after 30 seconds of reading. To get noticed, consider the following format, rather than a traditional letter:

1. Situation
2. Problems you experienced
3. Impact to Amex
4. Suggested improvements

Try to limit the entire letter to 1 min. of reading time and offer to spend 15 minutes on a conf. call w/ them to help them improve the review process. This is good because if they go for it, you can get passive aggressive on them and not show up to calls, continuously reschedule and eventually just not turn up.