I think it's entirely up to you when and if you feel okay about his seeing other women and especially the one that he broke boundaries with.
At some point I believe that your opinion and feelings will change one way or the other. Either you will be sure that you can't handle him seeing others or you won't and will have to act in accordance to your own health in the matter.
Good for you in your mulling it over and over... that is the only way to get to an end result and a sense of security. I hope that you act out of your own comfort eventually and in everyone's best interest.
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