Re: the last straw
Look, you need to make up your mind. If you are going to stay with her then stay, and stop doing detective work on the cell bill. If you are fun to be with, her texting will die down on it's own.
If you want to go, then go. Get on with it. But don't sit on the fence throwing stones. I would not check my wife's cell bill. If I thought there was a real danger of me being shafted, I would make a few financial arrangements and then forget about it.
The most important thing is how well you are getting on. Hell, if my wife was having an emotional affair at work without me knowing, and she was so nice to me that I thought we were getting on better than ever, I would not worry all that much. What I will not put up with is being made to feel 2nd best. Then I walk, simple as that.
You are working yourself up to fever pitch on scant evidence, if you happen to be wrong, you will come across as a fool.
I used to work at a place where there was a lot of flirting between married people. It got close to the edge, but really, it helped them pass the 8 hours more easily. I don't think any of them were "at it". Not only that, but they probably went home quite happily to their spouses, after a fun day at work. I would not have a problem with that. Loosen up!