I do believe if you want to keep the relationship going, and his other partner is not in play. He needs to feel and experience what you felt.
If he is a good friend and partner, he needs the experience since he hurt you. Who knows, he may find he likes it, and then it could be a fun extra experience for the two of you.
I do so very much hope you find the mix to make you super happy, and if he is a good guy in other areas, I hope he grows as a man.
You deserve all the good and authentic masculinity from your partner in the world.
If you need a suggestion for time frames for this "phase". Have him be honest and find out how long the cheating happened. Set it for that term, where you have the power to do what you need in your hall pass moment.