My C was pro marriage and agreed with most everything in Michelle's books. She did tell me that I needed to establish a time line for when to call it quits. She felt it was unfair to me if I waited around too long for my W to come around. She had seen others that had waited so long only to fail and be worn down emotionally by it all.
Now there are those that will say to stick with it for the sake of the children. That was a nobel and compelling reason for me to stick with it. However, once a wayward spouse starts to exhibit behavior that is a bad example to the children, I believe that is a time for me to put an end to it. Do you want your daughters to get the impression that promiscuous behavior is ok?
I think all hope in your marriage is gone. This is sad, but I really think you need to seperate yourself from your wife now. You love what you once had and it is so hard to let it all go. Try to get over the grieving. All I can say is that it does get better. But you have work on loving and respecting yourself.
If you do shop around for a lawyer, walk away from the bloodthirsty ones. For me, I was sold when I first met my lawyer because he spent the first half hour of our meeting discussing what was best for the children. He also understood that I still wanted to save my marriage if my W were to suddenly have a change of heart. And he was experienced and realistic. He told me up front that if something was going to court and it would cost me more in legal fees than what I would get in judgement, he would advise me as such.
Approach the filing for a divorce as not manning up or being a tough guy. It is just something you need to do so as to get sanity, dignity and happiness back into your and your kids life. As you go through it, try and stay with the high road and maintain friendliness with your W. It is what is best for the kids. Work out a parenting plan right away. If you can both agree without lawyers this is ideal. However, emotions can get in the way and that is when a lawyer or mediator needs to get involved. Treat the financials as a business transaction.
But most importantly, you need to be the rock of a dad for your daughters. I read something recently that says that daughters grow up and seek a man to marry that has similar qualities as their father. You also might want to look if you have any of the "Kids Turn" classes in your area.
Frank, you are a good man and have given excellent advice to others. I have confidence that you are going to get through this ordeal and find a happier life after it is all over. And hopefully your W too will come through it ok. There is life after divorce, but you have to make it such.