You are missing the point. You are STILL trying to control your W by hoping that a talk with a "pro marriage" person will turn her around.
Your BIL has no right to impose his views on your W or you and veil it with it the nonsense of it being his job as your best man.
Why do you find it interesting that they spoke for 45 min. and she didn't get upset? Your W is as crafty as they come and if you think she was going to show her true cards to your BIL then I think you are living in a fantasy world.
I have a very hard time understanding you. You always figure "something can't hurt" but you never stop and think about what could help. And the dinner with your BIL was not a helper.
You are still trying to mind read. So what if she didn't get upset for 45 min? Did you think she would and create a scene at a restaurant?
It should really bug you that your BIL feels anything to do with your marriage is "his job" because he was your best man. Why doesn't it? And, your W respects your BIL because of the reasons you stated before... he is successful at his job and that is the kind of job she wants. So, if she has to chat about you for 45 min. and keep it civil so she can continue to network about business with him, she will. She is rather transparent, no?
