IMO, don't respond.
Knocking out a text to you is nothing, a few key strokes, if he cares about your marriage why didn't he just pick up the damn phone? Or better still, say that to you in person. Why is it that one of the most important things in our lives, our relationships, are reduced to abbreviated texts via electronic means. Bah!!
Okay, got that off my chest....
Look at his actions honey.
He looked at the OW profile, then deleted his history.... why would he possibly think that doing any of that was going to do anything but damage further.
Why would he even look at her profile? This OW should be like poison to him, something to stay far, far away from. Not idle curiosity, not something to pass the time doing... why did he do it? Maybe because he hasn't yet realized the magnitude of what he's done, maybe a misguided sense of self-entitlement, maybe she still has some importance to him, he's not in a R mind-frame.
And as for guy's weekends away, yeah, no, that wouldn't be happening in my world, not for a very long time anyway, and why would he even want to? He should be focusing on your marriage, rebuilding with you, not having a good time with the boys.
MC, well, might be worth the effort, you could go and get all this off your chest, the MC could act as a mediator, then I'd leave them to it. But, might be better to ring the MC, update her/him of recent events, and leave him to explain it. MC is pointless if the WH/WW isn't going to do the work, isn't fully invested in the outcome, I don't think he's there honey.
Hugs.