Overall, I don't think you did that bad. I would give anything to have a R talk with my wife. In terms of agreeing with her decision to leave, your answer was right on. You stated that it is not want you want, b ut you are willing to support her if this is what she wants to do. This is not the response that she expects from you. It shows that you are being unselfish and giving up your needs for hers. Its the ultimate gift.
Arguing with her about wanting to leave only reflects the old you, the one who was only focused on himself. I know it seems counter productive, but you want to show yourself in a new light.
How long you can continue with this is hard to say. The emotional stress that you are under is not healthy over the long term. In my sitch I feel like I have a migraine 24/7. I constantly look at other people and imagine what it would be like to go home after work and have your loving wife waiting to greet you with a hug and a smile. Such a simple request, but one that seems impossible to attain. I have given myself a target of 18 months. At the beginning of may I will re-evaluate where I am and see if I can keep going on or not.
I think we both just want this bad dream to go away. Keep working on the family activities as much as possible. Your wife values this and you need to use this to your advantage.