I think that you two may need a little space away from each other so you can come to a conclusion as to how you want to proceed forward.
With so many years of marriage and so much at stake it only seems beneficial for all to have some breathing room. He cannot undo what has been done. You cannot change the scenario. The other woman really has nothing to do with the two of you and the life that the two of you have built.
I would not make any decisions on the matter until I had some time to think about what I really wanted. Are you willing to go speak with a therapist? Is he willing to seek outside help?