Something you may want to consider is whether or not it will help the sitch move forward or not. Will confronting WAW about the A help establish boundaries and gain respect? Will it blow up in your face on speculation about phone numbers? Will it push the A further underground? These are all things to consider.
I agree with this.
What REALLY changes if she is an affair right now? - I think in some states it matters, and in some it doesnt.
What would happen if you assumed that she is and she is not?