Well you asked, so here goes: Your BD on 10/1. You are in a trial separation for 30 days.
Today is Dec. 10 ... So 71 days after BD you're going on a date.
Why? What are your motives? Why does it coincide with a weekend when you know your wife is off with OP?
Companionship for the concert is nice, but how far is this going? Are you planning on kissing this woman? Doing more than that? Are you planning on seeing her again?
I'm pretty hardcore about two things: 1. being super clear that one thing is finished before you start something else - finished as in, your heart is free to start something else- and 2. check your motives.
Some people here will disagree and some people will agree. Ever hear the saying, "Opinions are like @$$holes, everyone's got one"? So be clear you are not taking a survey here and sit with this yourself to figure out what's going on for you.
I think it's fine to go to a concert with someone platonically. I think it's premature to date someone. Are you really ready to move on in that way or are you reacting to your wife's GAL weekend activities?
Also, a gentle suggestion: you may want to stop people in their tracks when they start volunteering her whereabouts. If NC is to truly work, I think it means putting the focus for 30 days squarely on yourself. That's hard to do when you keep getting reports on your wife's activities.
I thought this 0 Dark 30 thing was to give her (and you by extension) some breathing room to figure things out. It doesn't mean you are single and available for a 30 day trial run, or does it?
It absolutely stinks and hurts that your wife is off with someone else this weekend. Don't make the same mistakes. Make your own mistakes. Better still - learn from her mistakes so you don't drag a fourth party into the mix.
Again, just my thoughts. xoxoxo Wish Jack3Beans was here to offer some insight.
M 20+ T25+ S ~15.5 (BD) BD 4/6/15 D 12/23/16
"Someone I loved once gave me A box full of darkness. It took me years to understand, That this too, was a gift." ~ Mary Oliver