I feel for you. Resisting the snooping/looking for answers is one of the hardest things I've had to deal with as well because it will only make you worry. But it has to be done for your sake/sanity
I'm in a VERY similar situation during my separation with my wife. Without making it about me, my wife and I have been separated for a few weeks. An old friend of hers (who she hasn't seen in years but has Facebooked during our marriage) made some stupid decisions and went to jail for a couple of years. He just got out last month and he messaged her. He texted her a few times and she told me. Once we were separated, it was no longer on her to tell me if she's been texting him. When I left the house last night (we had a really good night) I thought everything was good. I get on Facebook this morning and she made a comment about something she did last night. He had a response that implied they at least texted or talked last night after I left.
But that is her journey and you and I can't change that for them. At some point sanity will set in for both of them (from what you say your wife is a pretty straight laced person who would never consider talking to a person like that let alone exhchange several texts). There really isn't a "bright" future with those guys.
To them, right now, they may seem like a better option than you and I. And it's up to them to come to thier own conclusion.
I've only been here a few days but this place provides SO much clarity and understanding. Stay strong.
Me: 33 W: 27 S: 5 D: 2 Bomb: 1/2/14 First Separation: 1/25/14 MC: 2/7/14 (one time only) Moved Back in: 3/31/14 W says she wants a divorce and moves out: 7/26/14 Appt to sign dissolution: 12/30/14