Mono, you sure lost it babes... remind me not to be demanding
wow, how nice that there is no negotiation... very controlling and manipulative no? Does she always treat you this way? It's bullshit that she is unable to not carry on into something more intimate with this man. We all have desire, we don't all act on that desire. To think otherwise is foolish, childish and naive.
I would suggest that she is in the throngs of NRE and has forgotten that she is talking to her husband. She sounds like a either a whiny child or a demanding controlling mother. That is really too bad. She could of approached this much differently as many people have on here... have a good long read.
At least you are in the same boat as others and there are plenty of resources here that hopefully can help you cope. Do a tag search for anything you are interested in... such as jealousy, boundaries, negotiations...and/or the like. You have a lot to learn and SO DOES SHE. This will not be poly unless she gets on the band wagon and starts sorting out how to practically love two men. It's all very well to say she does and that you should suck it up, but that is not poly. Poly is actively having empathy for and communicating with honesty, openness and respect. I guess she has the honesty down
I suggest that you start asking for your needs to be met, ask her what hers are and start negotiating the boundaries of this thing (I'm not into rules, again, more control and manipulation). You and her will find yourselves compromising in this and that is how it is for a time. Everything is different and changed now and that takes time to sort out. Don't ever compromise for the long haul though. You both deserve the best and should strive for it in an equal balance some how. Again, time. There is nothing but time to sort this out and she needs to respect that or your whole married life will blow up in both your faces. If she really loves you and what you have created together then she needs to remember this. She needs to go at your pace as you are the one struggling, another important thing to remember.
You are right, there is little to no benefit to you personally, other than having a new friend that shares two important things, the love of your wife and that he loves her two. That can be a powerful bond and can be very special. I suggest that you go and meet this guy and involve yourself in this journey that she would have you embark on.... this seems to yield the best results in the future. It is a bit of a wake up call too as fantasy often is faced with reality.
good luck. If nothing else you will certainly learn lots about yourself and your relationship with your wife. I hope you are ready for that challenge, because you are now in it, whether you want to be or not.