RCR AS I understand it, the Bible, and specifically Christian teaching in the Gospels tells us that we MAY divorce for adultery. It is not obligatory by any means. I often think we focus too much on sexual sin, and forget all teh other ways that we do wrong to each other. I do not condone adultery. It is a terrible betrayal of our marriage vows.
Forgiveness - well for a full and true reconciliation I believe that the adulterer has to repent, but they may not be able to do that until after they have returned, and begun to realise what they have really done.
Christ's words on the cross were to ask His Father to forgive his tormentors and executioners because they did not know what they were doing. Our Christian life should try to be an imitation of Christ. It is the hardest path, to forgive others, as we wish to be forgiven. As we move on with our Christian journey we start to realise the extent of our sinfulness, and be less judgemental and more forgiving of others . .. . For me it is a hard and rocky path. I am not a good forgiver, but I am work in progress!!