In house separation will be hard (mozza is right about my thread but I'd welcome any more advice/ideas). You might be able to control your behaviour but not necessarily how you feel or think. Like I said hard.
Don't send the letter. Letters generally bad no matter how well written. (Unless they are to yourself)
Both mid 30s, 2 young kids BD 7sep14 XW moved on long ago, now living with OM1 D paperwork in progress