How and when, tough questions with no single answer.
I would urge you to focus in therapy on the clarification of your values and needs, in that order. Until you have reached some level of clarity/certainty, I would recommend keeping this between you and your therapist.
That, of course, depends in part on what your wife already knows and her own values and needs. I would not take any of this lightly, and would advise being very cautious about taking steps that will certainly alter your live and may potentially inflict irreprable harm on your family and you as an individual.