NCB, I'm so sorry to hear about all of this. I know it must be very painful. She is definitely going through the denial and it's not my fault stages.
I'm a school teacher and I have a suggestion for you concerning your son. I suggest that you call his school and make an appointment to speak to the school counselor. I would go and talk face to face with the counselor and explain all that is going on with your family including the separation and the infidelity. Let her know that your W is taking sons around the other man and you believe this is the reason for the acting out. I then would ask her what her suggestions are for your son. Together you both can decide whether to share it with his teacher. Couselors can not repeat anything that you tell them in confidence unless you agree to it or the child is in danger.
I also think this would be a wise decision of going to see counselor in the event you divorce and there is a custody battle. I know too often the W tries to imply that the H never goes to school conferences and is not involved in the child's education. Start documenting everytime you visit with the teacher or the counselor.
Again, I'm so sorry for the pain you are going through.
Hugs, Yoyo
Life's challenges are not supposed to paralyze you, they're supposed to help you discover who you are. -- Bernice Johnson Reagon