Okay, OP, I'll help you out. This guy is just a friend, right? And has been for months? So it sounds to me like it's time for your wife to invite this fun guy over for dinner so you can meet him and see for yourself what a nice guy he is. There's no way she can refuse this reasonable request.
Now you'll be face-to-face with this dude on your own turf. An ideal situation. I'm getting excited for you just imagining it.
First, you'll play the affable host. Crack open some brews or a bottle of wine, get him to talk about his life, make some jokes, keep tabs on the dinner you're making and talk about how well it's coming along. Whenever he tells you something vaguely interesting about himself, turn your wife and say things like, "Honey, why didn't you ever tell me that about this guy! That's awesome, man."
(IMPORTANT NOTE: Regarding the dinner, you're going to want to make something that can be served individually. Obviously, the goal here is to get this guy to eat something that will have him sh*ttin his pants for the next two days. Make sure you practice beforehand so the ex-lax doesn't ruin the flavor.)
Once you've sat down to eat dinner and the guy is a little off his guard, you've got a green light to start ramping up the passive aggressiveness. If you're nice enough at the start, he won't realize that you're messing with him for a while. Start slow. Ask him about why he doesn't have a woman. Talk about your kids at length and how great your family is. Make note of the motorcycle and ask him how far into the mid-life crisis he is. Ask him if he'd like to take you on a romantic drive up sunset canyon.
(IMPORTANT NOTE: Now is also the time to have a friend come over and key "call (insert dude's phone number here) for quality bjs" into the side of his car. Then get a couple burner phones and send him a bunch of dick pics in the following days with the caption "suck on this, champ ;)")
Soon enough, he'll be suspicious, and your wife will definitely realize something is up. Now you break out the big guns. And I'm not speaking metaphorically. Buy a gun. Then tell your wife that you've been meaning to tell her, but with Trump's election and tensions getting high across the country, you thought it'd be better to have some protection when sh*t finally hits the fan. Surprise! Lift up your shirt and 'em your new glock. Give the guy an extra big smile at this point and laugh. Hopefully your wife will freak out about the weapon in the house. That's good. Deliberately get into a fight with her in front of him and rant about your responsibilities as the MAN of the household. Tell her that you fail to see how a gun is any less safe than, say, riding on a death-trap motorcycle. Tell her not to make a scene in front of your new friend. Then apologize for how everything has gone and tell the guy that maybe it'd be best for him to leave. After he leaves, pretend to have a come to jesus moment and apologize to your wife for the whole gun thing and blame it on the news getting you too riled up.
After two days on the toilet, getting his car repainted, and getting a bunch of dick pics, I'd be surprised if the guy wants to continue hitting on your wife. Let me know if he persists, and I'll help you gear up for round 2.