If you look through my posting history I do like to recommend to folks that they get angry and stay angry. It's a great state of mind for many freshly-betrayed as it fight's the betrayed's biggest enemy - complacency out of fear.
This is a common approach, and many people give this advice. OTOH, a lot of other people think that men in the US, at least, are taught to cover fear with anger. I did that for many decades, and I wasn't as happy or as effective as I could have been.
The best description of anger I’ve ever seen is 'the feeling that comes with wanting something to be different in your life'.
When you can't change the source of the anger, the best thing to do is to feel the anger and let it go - and then deal with the fear and grief that come along with the anger.
When you can make the changes necessary to remove the source of your discomfort, anger is a stimulus to that change, but focusing too much on the anger can keep one from realizing what we can change.
So my reco is to feel anger when you’re angry, but let it go when it’s done. Feelings are generally short-lived, so anger that comes and goes is often true anger. (It will come and go for most of us repeatedly, because a LOT of anger comes with being betrayed.) If you keep ruminating on anger, or if the anger hangs on, it may be that it’s hiding a different feeling.
I agree absolutely that it's important to keep fear from driving decision-making after, well ... now that I think about it, it's just plain important not to let fear drive decision-making. However, I don't know one can keep fear from driving decisions unless one feels the fear, acknowledges it, and takes it fully into account.
Some of the fears that hit Bses are:
The fear of emasculation/defeminization
The fear of being sexually inadequate
The fear of losing one's family
The fear of being ostracized
The fear of becoming an object of derision
The fear of the unknown that comes with changes
The fear that one is broken forever, unable to recover
The fear of staying an an M with no power
The fear of being alone
Etc., etc., etc.
If you cover fear with anger, as so many of us learn to do, there's nothing you can do about these fears. If you accept your fear, you can keep reminding yourself of your strengths and resources, and that gets fear under control.
For example, you can keep reminding yourself that your parts still work, that you found one partner so you can find another, that you're in great pain but you know how to heal, that you've always adjusted to change in the past so you can do it again, that your BS failed and you didn’t, etc., etc., etc.
Grief and Shame
It's important to take grief and shame into account, too. Many of us learn to cover one or both of these with with anger, but one can't deal with these feelings unless one names and feels them and starts to let them go.
Grief pretty much has to be felt to be released. Releasing shame usually needs some self-talk.
My reading (throughout my life, not just on SI) is that the people who do best are those who take initiative to analyze their situation and figure out the best outcome they can get. That starts with processing feelings, figuring out what one wants, what one willing to do to get what they want, the likelihood of success given the effort, their strengths weakness opportunities and threats, etc.
That works for BSes' recovering from infidelity. The WS plays a crucial part in the stay/go/temporize decision, but the SIers who process their feelings and work to get the most of what they want who seem to be happiest.
Bigger gets to the nitty-gritty for people who want R with his advice to tell one's WS, 'You can date and party all you want, but not as my spouse. Your choice.' In my own case, I wanted R with every fiber of my being. Luckily for me ( and for my W), my W did, too, and we were both willing to do the necessary work. But I also think she would have been out of my life if she had chosen not to do the work.
Bses – all human beings - need to go through pain to recover and live a good life. M is part of life. Sometimes one has to work very hard to rebuild an M or sacrifice the M to live one's good life. But I can’t imagine living in a bad M, and I would counsel everyone who’s doing to so to either change the M until it’s at least good enough – or split.
The earlier one accepts and works with one feelings about being betrayed, the faster one will heal. If you don't do that work, it's very likely that the feelings will fester and come out in ways that hurt you. And I think there’s already enough pain in the universe to add to it by selling oneself out.
As painful as processing the feelings is, it's less painful to process them than to continue carrying them around.
My strongest advice is to not let your fear of losing your family drive your decision. Don't let fear of screwing up your W's career drive your decision.
Frankly, I don't think your W knows what she wants. Telling her what you want and asking her to sign on may be exactly the guidance she needs to to make her decision. Infact, the low level of betrayal (this time) may be an indictor that she actually wants a real M.
Figure out what kind of relationship you want and go for it. If you want an open M, go for it. If you want monogamy, go for it. If you want to end this relationship with your W, go for it.
I know that deciding what you want limits your freedom. In deciding to want something, you must decide to give up other desirable possibilities. But M is hard work, and it will fail unless it's what you want to the exclusion of other possibilities.
I am really sorry you're hurting. The only good part of that is: you have the power you need to heal from your pain – if you exercise it.