vsecret,
I agree with JT, Farkel, and others. Don't send the letter.
Here are some of the reasons I have heard from you and others for sending the letter.
1. I want to put it all behind me.
Believe me, that will never happen. Residuals of your experience will be with you the rest of your life.
2. I don't want to be a hypocrite.
No you don't, but sometimes discrecion is better than valor. An opposing ideal to honesty up front, is the preservation of family ties. The longer you can maintain them, the more likely that they will bend the rules and maintain some contact with you.
3. It will happen eventualy. They will disfellowship me.
Not necessarily. If you play your cards right it might never happen. In your warfare with them, make a quiet retreat and prepare yourself for the next encounter. This is sort of like chess. If you carefully plan your moves you can win.
I am angry and want to tell them what I think of them.
4. Keep your emotions to a minimum and make them play by your rules not their's.
5. I just have to tell the truth about the truth.
If you have to talk to them "use tact" just like they do. In other words, lie your ass off to protect your situation. Short of that, be evasive in your answers. I know you can do that. You learned how to do that at the Kingdom Hall so you could deal with house holders in the door to door work.
Don't send the letter. You are letting them win by doing so.