There is no doubt that marriage is a serious topic with God. I know the position of the Church is that there is absolutely no divorce under any circumstances. However, I am reminded of where Jesus said, “But I say unto you, That whosoever shall put away his wife, saving for the cause of fornication, causeth her to commit adultery: and whosoever shall marry her that is divorced committeth adultery.” (Matt 5:32 KJV). Even God put away Israel for her spiritual fornication (see Isa 50:1 and Jer 3:8). It should be remembered, though, that God forgave Israel many times before divorcing her.
Anger is OK as long as you are careful not to sin (Eph 4:26). Jesus was angry when He saw the money changers in the Temple. He made a whip, overturned the tables and threw them all out, but He did not sin. Do not let the sun go down on your anger (not sure if it’s scripture, but it is good advice). Anger can fester and become bitterness, and that we are warned against ("Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble [you], and thereby many be defiled;’ Heb 12:15 KJV).
Forgiveness is something I learned very early in my Christian walk. Remember, we are told in the Lord’s prayer (among other places) “forgive us as we forgive others”. I have found that, when something happens and I need to forgive someone, rather than look at what they did to me, I will look at my life and consider how much God has forgiven me (remember the parable of the man who was forgiven a great debt, but wouldn’t forgive a small debt owed to him?). I light of what God has forgiven me, how can I not forgive someone else? There is no way anyone can trespass against me as much as I have trespassed against God.
Hope this helps!