Jim, just quickly. Strongly suggest you not sent. SIL doesn't need to know this. Clearly there is a different view and if SIL gives this letter to W, how will she respond? If you do want to send the letter then I suggest you leave out paragraph 3. SIL just doesn't need to know these details.
H 37 Me 36 Together 15 years Married 5 years No kids BD Apr 2014 H moved out 2 Jun 2014