I would also suggest a sit down (prepare for her to be defensive and BE prepared to handle it). Let her know that you have come to the realization that the living conditions you are currently dealing with no longer suit you and you feel its best for the family to proceed forward with legalities.
Your W views you as the obstacle to her happiness right now. So, remove yourself totally. Be polite and civil during this talk and under ANY circumstance do not fall back to any old destructive behaviors or patterns.
Before you have this talk you may want to research divorce/separation options in your state. Not as a threat but to show her it can be done in a fair, respectful and private way.
If she brings up money or any other issue that is tied in with divorce (custody, support) kindly let her know that the both of you can discuss it with the attnys to find the best solution.
If she starts to freak out (and she might just to see if you will resort back to your old ways) calmly end the talk and let her know when she is ready to discuss this in a more productive fashion ya'll will continue. Thank her for her time.
