Devastatedhusband, it seems to me, from what you've written, that your WW is on the fence, unable to decide if she wants her husband or her boyfriend (and it's entirely possible she wants to keep both). If that's not acceptable to you, then make a choice for yourself.
Look, brother, I know how hard it is to survive infidelity. We all do here. Right now, you're still in shock. That's perfectly normal and expected. I think it took me a good 10 months just to recover from the shock of it all and to start feeling like a semblance of my former self. I also lost about 30lbs in two months. I couldn't sleep. I couldn't function normally. I'd walk from one room to the next and, by the time I got there, I'd forgotten why I was there. My short-term memory was just gone. My emotions were all over the place, too. I could go from feeling rage to anguish faster than I could fart. I didn't choose my username to be cute. I really was un-fucking-hinged.
As others have pointed out, you cannot control your WW (or anyone else for that matter). She's going to do what she wants to do, regardless of how it affects others. The best you can do is make good choices for yourself. If that includes not be married to a cheater, then so be it. Let her know, in no uncertain terms, that this isn't the sort of marriage, or life, that you want for yourself.
If you haven't yet done so, please take some time to check-out The Healing Library. Inside the "Articles" tab, you will find a wealth of excellent essays written by veteran SI members. In particular, I would recommend: "A Tactical Primer;" and "Understand the 180."
Your most important goal right now, I believe, is to take care of yourself. For most people, the betrayal of infidelity is a profound shock to the system and a severe emotional and psychological trauma. In all of the years I've been a member here, I've never ceased to be amazed at just how hard and how deeply it hits people. Focusing on you and your recovery will be your first steps on a very long and difficult journey towards healing (we're talking years, here, brother).
Force yourself to eat small, healthy meals. Stay hydrated. Avoid alcohol and recreational drugs; they will only prolong the pain. "Hit the gym;" the endorphins and hormones will help you to recover and heal (and feel a little better).
If you can't sleep, try a mild OTC sleep aid. If that doesn't work, consult your doctor. Let him know what's going on in your life. There's a good chance, especially if he's up there in years, that he's heard it all before. He may not have the best life advice, but he'll certainly have some good tips on how to stay healthy.
When you do consult an attorney, ask him if he's had clients in similar situations. He may not have the best life advice, either, but he'll certainly have a few good legal tips.
I'd also recommend consulting a good therapist (finding one isn't always easy, btw). As with any doctor or lawyer, they might not always have the best life advice, but they'll certainly have a few good tips on how to recover and begin to heal.
Do not blame yourself. Most betrayed spouses, because they're in shock, will blame themselves, ponder what they could have done differently, and wonder "why me?" And that, too, is natural and to be expected. Our brains are wired to learn from traumas in order to avoid similar traumas in the future. The truth, however difficult to accept, is that nothing you ever said or didn't say, nothing you ever did or didn't do, would have made any difference at all. Your WW's affair is 100% on her and her alone. Her affair had absolutely nothing at all to do with you and everything to do with her own inability, or unwillingness, to deal with her own issues in a healthy manner.
You've got a long road ahead of you, sir. It will not be easy. It's not a linear process. It will take a lot of work on your part, which is why I stress the importance of taking care of yourself, focusing on you, your recovery and healing.
Keep on reading and posting here. This community saved me. I don't know how else to put it. The support, guidance and wisdom I found here was beyond my wildest expectations. Some of the responses you'll get will resonate with you more than others. Some of it will be "tough love." Some of it might piss you off. Some of it will help you to open doors you never even realized were there. Some of it will lift you up.
Peace, brother.