Hugs to you, friend. You did a great job in DB'ing. You stayed calm, you validated her and you didn't react to what she told you. I know you're beating yourself up right now (you shouldn't - you've already been doing that for months!)... but remember to pat yourself on the back too. Not many men could have had the conversation you had last night and rised above jealousy and anger to show love. I think you did an amazing job.
As for the PA and forgiveness.... you know my sitch and know I'm struggling in the same place right now. The "I was done" line must be the mantra for those WAS who have PA's or EA's. I'm actually jealous that your W is honest and you have the truth! Your intuition was right on too. I know it's hard hearing the truth (been there, done that with the XH)... but at the same time, hearing the truth doesn't mean that it happened. It already happened whether you heard the truth or not. Now you can face it. You do have an opportunity here for peace, closure and moving forward with both of you forgiving your past mistakes, both of you changed, both of you still in love with each other and wanting to move forward. One word of advice from someone who has been there, don't ask for details. The basics are enough, trust me. Once you have an image in your mind, you can't get rid of it so leave it alone. It happened, you know it happened, that's really all you need to know. Anything more will make forgiveness harder.
You do have a second chance here... what do you want to do with it?
Me - 38, 2nd M, no living children, 1 forever 6 yr old boy H - 44, 3rd M, twins 16
Dating 4/07 M 10/08 Bomb #1 12/10 Bomb #2 1/11 Bomb #3 12/11