Realizing you are poly, especially when you are already in a relationship and your SO doesn't take it well, is never a fun place to be. For that reason, I am glad to hear that Steve's reaction was not one of complete shock and despair. He offers a glimmer of hope that things can proceed with Lynn without the Universe imploding in on itself.
I wish the same was true of your wife, but not everyone is that lucky. It sounds like there are tough decisions ahead of you.