Good for you Yorkie!! Your comment about the yellow room made me laugh outloud. Thank you for that.
I agree with everything FS said. His anger is all projection. He knows what he is doing is wrong. He wants you to justify it by being a b***h. Do no give him that! Just be your strong, graceful and dignified self. Do not get drawn into a defensive tit-for-tat argument. Validate as much as you can. If he is a total jerk, tell him that today was obviously not a great time to meet and take your leave of the situation. Do NOT agree to anything. Tell him you need time to think [and consult a lawyer]. Don’t let him bully you into anything.
The OW sounds like a definite affair down. He will come to realize that in time and like FS said, hopefully you won’t care. However, I know how much time 30 years is and that is a lot of history to just close the door forever. Keep GAL. You will be happy you did regardless of the outcome.
Hoping beyond hope that your meeting goes reasonably well. (((HUGS)))