I don't believe anyone ever just "let's go" of very hurtful stuff. So I don't think that there is a formula for doing that. The best you two can do, if you want to stay together, is to recommit and then see how that goes for the next year or two.

You'll let go of the past, if you see real change in the present. You've both strayed from the relationship. It seems like you two don't really value "exclusivity," so I don't see where the motivation is going to come from to be faithful.

While you feel that your straying while on the road was very different because you told her and got her permission, it's not as different as you think. When you did that, you communicated to her that you were not 100% devoted to her. Regardless of what she said to you about it being alright, I promise you it did not feel good to her to know you did that. To some extant, she has been kind of evening the score. That's what tends to happen.