Sorry. The situation is awful. There's no doubt it's stressful and painful for you all.
Originally I wrote something insensitive. My apologies.
Still, I hope you take this time to care for yourself now as well. Please give yourself time to think on what you want to do with the situation.
I agree with grubs.
You do have a problem. You don't know the woman she was around him. Now are wondering which woman is reality. Or at least closer to it.
There should be fallout. If you hadn't found anything, maybe the fallout would have been directly at you. You were driven to verify by her off behavior about him. You found evidence your wife actively chasing a co-worker. That she was having sexual conversations with that man. She was diverting time from you to going to spend it sexting and connecting with him. Marriage shouldn't have secrets like this.
4. Gather more data.
I'd recommend 4. All of the others will leave major doubt in your mind about what exactly you are dealing with. Did she just let some harmless banter get out of hand or was she really seeking an full blown affair that her texts appear to show.
You seem like you would like to know more. Obviously, it would be great to confront and talk it out like a person would in a healthy relationship situation. You know it's not that. She's been keeping things from you and likely won't tell you anything when you do approach her, no matter how you approach the conversation.
At the very least, take the time to decide what you want depending upon what you know and how she reacts to your conversation. Think it through and plan as much as possible. What will you accept and what won't you accept?
It sucks. Sorry you are dealing with this.
(Edit: My original response was not very empathetic or kind.
[This message edited by KitchenDepth5551 at 4:30 AM, Friday, August 29th]