I agree with what a lot of people have said here. Basically, I think that you have to get your relationship with your wife good before you open it. Opening it tends to cause new stress at first, so you need things to be good.
I think you both need to come out and say what you want. Let it be in a way that you are both free to say what you feel without judging each other. Just figure out your needs.
This other guy your wife likes is not into polyamory. He is operating under the idea that you have to possess the one you love. If your wife wants to get involved with someone, it should be with someone who can respect your relationship with her.
i wish you the best.