So Are They Now Even, And Go From There...
I feel any judge would award him custody of the child no matter how much is given/written to a child is better with the mom. With this in mind I may be alone in thinking these two might "well not forget" but maybe forgive for the sake of the kid. They both went overboard with there actions and despite how cruel she was he still under estimated her love for him and the hurt she suffered, just as she needs to understand she went way overboard with her revenge plot.
If they divorced I see the hate becoming even stronger as one will have a life long grudge against the other and maybe transfer it to the kid. There is no way when the kid goes from one parents household to the other the hurt will not start up again.