Kaya, I'm glad you can see your XAH in this light now. You've gone through so much pain. The situations he's put you through are ridiculous and unfair.
I'd agree though that it was excellent therapy to write this letter, and maybe you should continue to write these letters to get rid of all the pain, but that you should burn it or shred it. It would be satisfying to send it, yes. I've learnt via the divorce from my first XH who was a sociopath that stalked me for years after and my deceased AH who was extremely violent towards me, that sending advance notice of what you are intending to do could be dangerous for you. Of course he knows you are divorcing him. Don't make it easy for him to avoid getting the papers, or head off whomever needs to be notified or send more of his friends to harass you.
When you do send the papers, include the simple notice," Do not contact me again."