" I will be cheating on me" from your statement, you are truely cheating on yourself. This is exactly what Devil want to achieve in marriage, to make this sinful act be like "a normal thing". My sister, I advice you think twice now before it is too late. Yes, what the man did is bad but I think there could be a better solution.
I think repentance should preceed forgiveness... if the person you are forgiving 7*70 times a day did not repent, what is the essence of you forgiving him... May God deliver us