I stand corrected, he is a predator of sorts. I guess my point being it is neither here nor there when it comes to your M. Your W made her choice, she is a grown woman. He is clearly not your friend and just a crappy person.
As far as exposure as a threat? Do you want to threaten your W back home, or do you want her to come home and recommit to the M because it's what she truly wants to do?