Frank, I think I read a while back that your W said she was going to date. It does not matter now if she currently has a boyfriend. Your logic is correct - why did she not deny it when you told her that if she is dating then she needs to move out.
She is telling D17 things about your marital dispute that should not be said. It sure seems that she is trying to alienate them and turn them against you. You on the other hand did the right thing in not telling D17 about the past affair. Shelter them from this as much as possible.
I worry that your D17 is feeling responsible now for the separation. You probably need to reassure her again several times that she did not influence your decision.
