At the moment the OM is the knight in shining armour as he is helping to make the hurt that your wife is feeling in the marriage go away. Once he removes his armour then he is just an ordinary man with faults like anyone else.
Other OP's are right, you need to start setting boundaries for yourself. Read Sandi's WAW thread on Cadet's homework and if you can maybe speak with a DB coach to help you set these boundaries. At the moment you can't stop her from doing what she is doing but you can help yourself.
I know at the moment you desperately want an end to this so starting D proceedings sounds like the obvious answer but if you really want a chance at saving your M doing this will just play into her hands and make it easier for her. If she wants D then she needs to do all the leg work, don't do a thing to help her.
Also as you are living together still you have a great opportunity to do done 180s. For example if you haven't gone out on your own much before then start doing that now but don't tell her what you are doing or where you are going. At the moment it sounds like she is swanning of out and expecting you to stay at home with the kids. Beat her to it!
Me - 47 H - 45 D-16 M - 6 years Separated - May 16
Don't leave me behind can't you see me I'm shining... (Years & Years - 'Shine')
