You are not ending the marriage by seeing a lawyer. You are seeing a lawyer to make sure you protect yourself in case your marriage ends. You leaving is because it's what is needed for your sanity. You wife has zero respect for you. None. Trust me I know that hurts. I feel terrible that you are in this position. But she is openly carrying on an affair with someone else. It doesn't get more disrespectful than that. That clearly should be a boundary for you, unless you ok living in a marriage with the three people and you being the person that is being pooped on constantly.
You are leaving and dropping the rope. You have to if you want any shot at all at saving your marriage. And you need to do it for you, not her. That's the hardest part. The part that in the end DBing is for you. Not to save your marriage. It will only give you a small shot at saving your marriage.
I promise you that leaving and going dark is the only way you will have that shot


M 37 W 30
S 7
Together 10 years
Married 9 years
BD: 12/12/12(W filed same day)
I moved to apartment 1/11/13
W and S moved to MIL 1/11/13
Peicing: 6/3/13
Reconciled: 7/2013
BD2: 4/20/16
still working on it