Quote: I can almost guess that if I confront him he will say I was just looking out of curiousity. Like it's no big deal and don't mean anything.
That's almost certainly what he would say. I've only read a couple of your posts, and haven't read your whole sitch, but I can already say this guy sounds profoundly immature, despite his age. I think you probably realize that a married man who is repeatedly checking out dating sites and researching women in his area is not "just curious".
Sounds to me like he is unwilling to face up to the problems in his marriage, and unwilling to work on that (immaturity again), and is looking for an easy out, or for a "have the cake and eat it" scenario. Sounds like the two of you need some serious discussion time, and probably counselling as well..