I am glad to hear that you are working on boundaries, as that seems to be one of your key areas (it takes one to know one).
When it comes down to it, boundaries are just about defining what's hers and what's yours. Her choices are hers, and you can't do anything to change them. Your choices are yours, and she can't do anything to change them.
If she wants to leave the family for OM, that is her choice - it's on her side of the boundary. If she wants YOU to leave the family so she can be with OM, she is trying to cross over and steal something on YOUR side of the boundary! Which can only happen if you let her do so - she may come over and act as though everythign belongs to her and she has the right to dictate what happens, but she can't dictate unless you capitulate.
As far as partenting goes, even though the two of you share taht function, there are still boundaries. There is the influence she has over your children, and that influence you have over them. She is using her influence to tell them, whether they realize it or not, that a woman has the right to decide she can do what she wants, regardless of her marriage vows. The way you respond will determine the influence you have over the children. You could become vicious in fighting against her behavior, telling your children that revenge is your perogative once you have been wronged. You could go to the other extreme and give in to her on everything she says, not allowing her to experience any of the consequences of her own choices, thus telegraphing to your children the idea that a woman has all the power in a relationship and can do what she likes, and that the man is obligated to pay the price of her actions (that she herself has no obligation to pay her own consequences). Or you can hold your own, recognozing her ability to make her own decisions, but mot rewarding her for such behavior, and not supporting it.
I think your idea of saying that you will n ot support her A by letting her use your computer to carry it on is a small but excellent example. Another is reclaiming the bed, which is as much yours as hers. (Yes, I realize that I aam sleeping separately fromn my W right now, but it is for different reasons and under different circumstnaces).
I agree that trying to kick her out is not necessarily a good idea (DR has a thing or two to say about giving ultimatums), . Saying you will not move out, nor will you resign custody of teh kids to her just because she wants them and wants another man at the same time, on the other hand, keeps you on your side of the boundary and stil gives you a powerful stand.
Just some thoughts.
Think about it...if you met a potential mate who was nothing but a bundle of needs, would YOU be attracted to them?
