SRT, I loved three of four paragraphs. But when you tell her how to run her love life...too much, guy! Tell her you are confident she will lead her life in a way that is healthy for herself and her family or whatever way you put it BUT don't tell her what R she can and can't have or threaten violence, even as a joke (custody, remember, and this is in writing!). Also I wouldn't tell her you're open for a little boffing, it's confusing. Otherwise, it is a beautiful heartfelt letter and will bring her to tears, I'm sure of it cuz I'm almost there myself!
