He's really getting big. Only 5 months and close to 7 pounds, and none of it fat.
On another note, she's coming down with some bad cold or a bug and blaming it on him, but I would think if she was allergic it would have happened before now, since he's been here 4 months. I'm hoping it runs its course soon and goes away, because if it doesn't, I'm still going to have a tough argument for keeping him.
I don't think it is allergies, like you said it would have been an issue earlier. It is probably a cold, but if you want to make her more at ease you may try something called Allerpet or something similar to wipe the kittens fur and remove the dander. They also have sprays for furniture carpet, etc. I have never used it but I have heard of it. I am sorry your wife is getting sick, I guess it is starting to be that time of the year. I hope she gets better soon.