I confronted one of my abusers & the situation was very different. I was young & did it more out of revenge. I confronted him the night before he got married.
Touché.
Put what you need to into the letter. Seal it. Hang onto it & see if this act brings you closure you're looking for.
Then ask why it did or why it did not. Then decide what you'd like to do.
If you're not expecting anything from him....what if he does decide to reply. Are you ready for that.