mind if one of the ladies speak up for a bit here fella's?
RG - I first want to say kudos to you for trying, more than anything else that you are simply trying is awesome
to the specifics - what is bothering you most about your current situation? have you told your wife it bothers you? has she responded and tried to make it less bothersome or asked how she can help make it not bother you?
do you yourself have an interest in talking to her other guy? does she want you both to talk? do you feel some obligation to get to know him?
do you yourself have any interest at all in finding yourself someone else while still with your wife? (trying to understand the whole situation and i can't recall if you've mentioned this before or not) if you do want that, would your wife mind?
of everything right at the front of my mind of what you said, you seem to be trying to be supportive and are concerned your not being supportive enough or afraid your wife wants more, I'd simply say be as supportive as you can, don't make yourself uncomfortable or unhappy, and remind her you want things to move as slow or fast as you can handle and she should respect that
as to the other guys wife knowing or not knowing, well in a perfect world and perfect relationship, all involved would know everythign they need to do, we humans are quite often so very far from perfect, and forgive me to any this will offend, but simply put, if the other guy isn't up front or concerned about being up front, then i really fail to see how this could in anyway be your problem, its really on him, so i'd say try not to stress over that since it really is out of your hands
as to what happens when and if they met in person sometime and how physical they are, well, i'd suggest you and your wife sit down, talk this out decide what your okay with and not okay with, and ask her to respect your wishes
again its very wonderful of you to be giving this a chance, I hope she appreciates it, but don't make yourself upset over things you can't do anythign about and don't let yourself be hurt, it should be give and take, tell your wife what is and is not acceptable to you and she should respect that, lots of luck and well wishes to you and yours