Pfft - He's lying re talking to her and 'Googling' her. He asked where she works and she told him. Simple as that. They have been having normal every day conversations as well as the smutty stuff. He knows her name FFS. And I bet he knows a whole lot more too.
He has more to reveal. And he will. He will also contradict himself an awful lot so my advice is to make a note of what you find, what he tells you, etc so that he doesn't try to trip you up or back track.
I'm so sorry that you are going through this but you have to switch to survival mode IYSWIM.
The email entitled 'shit' was to her. I'd bet anything on that.
He's very sorry I'm certain, sorry he got caught. If he hadn't I think that he would've carried on. And taken it to the next level.
You need to find out how far this has actually gone and just as important, how far he wanted it to go.
He has nothing to lose now, the cat is out of the bag, the damage is done so why not just get it over with and tell you everything?
But he won't. He still thinks that he can hold a little back and everything will ok.
I don't think he wanted to hurt you, he wanted his cake and eat it. He got away with it for as long as he did but his luck just ran out.
And now he has to realise the gravity of his actions. The fact that he stands to lose you and his home life, his safe little world that he came home to each night, seeing his children every day, put them to bed each night, his comfort zone. He stands to lose it all but he never thought he would.
Which is why he is playing this down to you. He is shitting himself now that he understands just what he has done.
So the chances are he won't disclose the truth to try and lesson the blow.
But you can't do anything until you know it all. All the gory details. The lot. Don't let him bullshit you. Then again, I don't think that you will!!
Sorry for my ramble 