He is apparently terrified of me, or doesn't think I could possibly be ok with any of this happening, and that is really not what I want. I actually think it would be easier if him and I were friendly with each other and could talk openly about this all. My wife fears that he won't be up for such a conversation, and that bugs me.
He could imagine all kinds of things. But he cannot KNOW where you stand until opportunity is created for your to TELL HIM where you stand. If he thinks he wants to start something with her and grow love there with her? But he cannot hack a simple conversation with her other Sweetie (you) to get boundaries in place so it can all go well? Wife could consider what kind of start she's giving her potential polyship. A solid start or a flaky one.
Why does she fear he won't be up for a conversation like that? Because she can already tell from limited experience of him that he's behaving all flaky?
Could not let eagerness to being polyshipping cloud judgement. She's already been hurt. Why would she want to take up with more flaky man action? I am confused.
What about him and his situation makes him a good polypartner for her? Has she articulated that? What makes him yummy cookies for her?
In your shoes, I don't blame you for being concerned about shenanigans yet to come.
I just get the sense he is wanting to walk into it eyes wide shut.
Are they really "eyes wide shut?" Or could it be you being around in conversation wrecks his smoothie talkin' at your wife? She's all starry-eyed with her crush on him and maybe not seeing clear. You aren't crushing on him and looking at him with a different view. Could that be why he doesn't want to play on the level and does not want you around to wreck his game?
I'd suggest proceeding with caution. Both you and wife.
If wife (and you) are seeking one kind of polyship model and polyship standard he's after another kind -- could call it "not compatible" and let it go.
Your wife deserves someone who really wants to be with her. Not lukewarm. Certainly not lukewarm with a side helping of UGH factor to boot.
My 2 cents,