Garrett,
Don't write a letter. It will only make things worse. Just leave, or better yet--since you haven't gone to a meeting in 2 weeks--just stay away. Don't go back.
Fading is a slow and painful process. Simply stopping is much better (although not everyone can emotionally pull it off).
When the elders do start hounding you say something like, "I told you, 'I'm depressed,' please just leave me alone."
If they ask anything else, especially "loyalty questions," just repeat the above.
I recommend reading Steven Hassan's book, Releasing the Bonds. It's very helpful.
Best wishes,
Oubliette