No, you did really well. It feels worse because there is conflict here and she is getting upset/mad and you don't want your W upset. No one wants their spouse upset.
Yes, you are stoking the flames to start getting something out. Better to do that, then to let the flames die out on their own and not do anything.
She will not want to talk Saturday. Heck, YOU dont even want to. This is really tough. Things will be faced very clearly and this is hard for both of you to do.
There are 2 big reasons you need to have this talk. ONE- You are resenting her and getting really angry at her and if something isn't done soon you will hate her forever and move on yourself. TWO- She is moving out and doing so without facing the reality of it. She is still seeing the OM, and the marriage has no chance if she is still seeing him.
The main thing is be calm and strong and try to not get angry. Ok, yes you can't focus on just her being the problem. Yes, you say you BOTH need to work together. THe focus is on her choices right now. She needs to state her choice as plain as day. Look back at the questions I said you should ask her. If she cannot do those things, you will not be able to work on the marriage. Look back at what Kat had said, too. Get the clarity for you and HER. If she chooses to stay with OM and leave the home, tell her exactly what the consequences of that will be and begin those consequences immediately.
She will not be running to you with open arms saying "I want to work this out with you." That is not going to happen. Expect it to be less than romantic. The whole thing is awful. She has cheated on you, she feels she doesn't love you, she is miserable, you are miserable, BUT she has to CHOOSE to TRY one last time and the only way she can is if she has no contact with OM and stays in the home to work WITH you.