I'm going to try to provide some advice, and then later some comments.
The Advice - Slow down. Decisions made in the heat of anger and other emotions are often short-sighted and wrong, and are often too much response for too little reason. Right now your entire personal world is consumed by this, and you are hurt and confused. You are like an animal that had been backed into a corner and the usual response to this is to lash out at what has caused you pain. This is a perfectly normal response. And the normal action following this is to hurt that which has caused the pain. Understand and accept this - but that doesn't mean that you have to act on it.
I have some important questions. Do you still care for him? If so, do you care enough to give each of you a chance to try to work this out? Are you willing to be brutally honest not only with him but also with yourself? What I have learned in life is that one old adage is true. That there are three sides to a story - his, hers, and the truth. I am NOT dismissing what he has done. Even though a friend of his forced the issue, at least you heard it first from him and not someone else.
You stand at a crossroads now. You can do as many have suggested and go completely no contact, kick him out of the house and try to completely control the situation. You've both been through divorce and you know that this will most certainly "poison the well." This is the advice a lawyer would probably give. Works well for them - they charge by the hour. Or you could do the human and humane thing - sit down and actually TALK HONESTLY WITH HIM. You mention you're in your late 40's and I'm going to assume he's a similar age, and you've both been divorced before. So you both came into this with enough baggage to take a guilt trip around the world. He made a mistake. Is it one you can forgive? I don't know - this is your decision to make. I'm not going to call him a despicable person, because other than your words I know nothing about him. I do know that you at one time you saw something positive enough in him to want to spend you life with him. Is he a human with his good and bad points that made a mistake, or has he taken a serum to change him to bad evil person like so many here want to paint him?
Here's another side of the coin - some of this is your fault. You and so many brought up the number of texts from him. But you also mentioned at at the beginning of your relationship you would get panic attacks if he didn't respond quickly enough. By your actions you created and encouraged this response. You also stated you went from a long abusive relationship to this one very quickly. This is not uncommon, but it also means you never had enough time to truly deal with the long term effects of your previous marriage. I'm going out on a limb here but based on the panic attacks over communication (texting) and the other questions you have posed you might fit the anecdotal description of "emotionally needy." I have no psychological training to determine this - just my personal gut feeling about the comments and information you have provided.
I would recommend personal counseling for you, because of your past marriage, whether you and your husband decide to work this out or not. I would also recommend DivorceCare for both of you, but likely separate groups. I went through it during my own divorce and this was the thing that helped me the most. It helped because I found I was not alone in how I felt, in some ways was better off than others, and that I can get through this. My gut tells me that if you both try this it might help save your relationship.
Suggestions over , now comments. I've read to many posts in this thread on hide this from him, don't tell him about that, protect your self first and the marriage second. She's been hurt and angered buy what he has done and him hiding it, and the response is to do things that would escalate and antagonize the situation and hide it from him. This is not how to work on a relationship - this is how to guarantee than one in stress will almost certainly fail. It seems that marriage is considered a disposable item, and may explain why it's at an all time low since they started keeping the statistic in the US 118 years ago. It's disheartening.