I agree that you most of all need to stop comparing yourself to him, and that she is caught up in the heady euphoria of what is called NRE. Also agree that moving him in with you seems to be too much too soon. Take back your house is right! You know you can work out a schedule so she can spend half the week with him, half with you.
I've never seen anyone talk about a V as compared to a checkmark, as if the length of the "legs" in the V or checkmark represents the importance of the person at the hinge. You must be very visually-oriented.
I must say I have never been able to understand the mindset of someone being okay with their spouse having "no strings" sex, as if she's a toy, but not being okay with the spouse developing deeper feelings. I can't say what your wife has with this guy isn't really much more than sex, though, but wouldn't you want the person you love to have a life filled with love, whether from friends, family, or lovers, rather than just recreational sex? It doesn't diminish your love or your value to her for her to find love in more than one person.