I like your letter, but its hard to go dark without any type of custody schedule. Without a schedule, you will get dragged into constant back and forth negotiations. Of course trying to make a schedule now will lead to a lot of contentious arguing in the near term.
I think if you declare outright that you are going to limit communication with her, you need to first be in a position to ensure that you can actually follow through. I would suggest that you either delay this announcement until after you work out a schedule and terms of a more formal separation or divorce, or use this as an opportunity to push for the implementation of an agreement or order.
