@user1493423934 My goodness, you are so vindictive and sound insane. Did you even think about what you suggested there? Just despicable.
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OP, your husband is wrong for starting an affair, without doubt. Your hurt is also understandable, but it's clear now that the relationship has ended and you two are to go your separate ways. Therefore, although legally you are not separated, you two are no longer together so he is able to go ahead and continue to live his life.
I understand you are hurt but the fact you are wanting to do something to cause issues is not reasonable and it is wrong for you to ask for ideas. If I am honest, if you were a man and you were asking all of this, you would have most definitely been called abusive and would have had a stream of responses calling you out.
You do not want to separate, but ask yourself why you should be with a man that would hurt you by starting an emotional affair, and one that does no longer wish to be with you? Value yourself and your life higher than what he brings to the table. You deserve better and you should want better for yourself.
Be patient with yourself and kind to yourself also, do not allow his actions to make you a person you do not wish to be. Heartbreaks are painful, but the end of this chapter means you can start a new and better one.
Let him do what he wants, and you begin to do the same for yourself. Start focusing on what you need to do to move forward and surround yourself with a good support system - I do hope you have one?