Remember that this guy is probably shitting his pants about now! Geesh, he is in a far worse place than you... empathize with that. If you are feeling stressed, no doubt he is too and the two of you can relate.
Maybe make a joke about it when he comes in the door. There is nothing like being entirely honest and saying to him that you have been really freaked out because you want him to like you because this woman and what you are developing with her is important to you. You care about her and who is important to her and REALLY want to make a good impression because he means something to her... I would be surprised if he didn't feel safe enough to be just as honest back with you. Being open and vulnerable creates space for others to be so.
I don't know if it is such a good idea to be keen on your wife developing an interest in him. I think its disrespectful to even think about it in terms of a solution. The man claims he is mono, I would leave him alone on that one until he suggests otherwise.
I would be damned sure, if I were her, not to flirt or think of him in a sexual/relationship way at all. I think I would be a good host and make him feel welcomed and comfortable. That's it. The guy has enough on his plate trying to comprehend the lifestyle he is being forced to understand without complicating it with people coming on to him or offering him something other than a warm hand of friendship. He is your metamour, not a potential lover at this point.
I would suggest doing some reading on here about mono/poly relationships in order to get an understanding of where he might be coming from... the two are VERY different and I have found no way to merge the two without compromises that can be really difficult. I am in a live in relationship with Mono and PN, one my mono boyfriend, the other my poly husband. It is very complicated and in order to be respectful, I suggest knowing something about it. Being openly poly/swingerish can come across in a certain way to a lot of mono folk. If you really want this guy to feel comfortable; I suggest really knowing and thinking more on that.
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