Well, I am not a Mormon either. (See earlier question.) My father is angry with me because I told him I thought that his buying a 34 year old woman $209.00 in clothing at Nordstrom's department store was not proper. My mother is in a home with Alzheimer and he is spending her money on another woman. Not only that, but my mother worked for him for over 40 years in his business without a paycheck or even getting Social Security. They were both raging alcoholics until they were well into their 60's and then they were forced to quit drinking or die. My father is a bully; he bullied and verbally abused my mother and all three of his children. He is spending money on this woman that we need to take care of my Mom. But he just said, it's my money, all my money.
My sister and I left home as early as possible. We both married looser type guys just to get away from their abuse. My brother joined Vietnam after he and my Dad got into a fist fight in our front yard. He lost his leg, his mind and ultimately his life. My sister smoked and drank and she died from lung cancer at age 47. So I am the only child left.
I don't smoke and rarely drink. I have tried to love my parents because the Bible says to honor them. I just can't take my Dad's verbal abuse. He refused to go to my sister or brother's funerals. I buried them without any family except my own daughters. I am really tired of his verbal abuse and selfishness. I just don't want to go around him any more. It is really sad as he is 80 years old and alone, but he has brought it on himself. I am just going to stay away for a while. He has never told me he was sorry that he was a poor dad. He just blames his behavior on his mother whom he never spoke to for the last ten years of her life. She did not do anything to him according to my Dad's only sister (to whom he does not speak) except remarry after my grandfather died during the depression. He is self-centered and his sister says he has always been the same and feels sorry for me. I am really upset about this situation. He is old and should be nice to his last remaining family member (me) who speaks to him.
You noted that your parents have lived a sinful life and that your father has never changed in all his years. It is truly sad that he hasn't mended his ways. However, you must understand that a person's behavior is the result of his or her own choices. He can't blame anyone but himself for the the life he led or the life he will lead. "The soul who sins shall die. The son shall not bear the guilt of the father, nor the father bear the guilt of the son. The righteousness of the righteous shall be upon himself, and the wickedness of the wicked shall be upon himself" (Ezekiel 18:20). It would be wonderful if he would change, but you must understand that you can't make him change. You can encourage him to go in the right direction, but he must decide for himself.
Yes, you will have to back off and let him face the consequences of his sins. Honoring your parents does not mean supporting them in their sins or bringing their sins into your life. See "Honor Your Mother and Father" for more details. Be polite to him when you must interact. Check once in a while to see that he is all right. But when he becomes abusive or tries to drag you down to his level, just politely tell him "no I won't go there" and hang up or leave.
Many people mistakenly believe that Christ requires his followers to forgive and accept people as they are. "If anyone sees his brother sinning a sin which does not lead to death, he will ask, and He will give him life for those who commit sin not leading to death. There is sin leading to death. I do not say that he should pray about that. All unrighteousness is sin, and there is sin not leading to death" (I John 5:16-17). This verse confuses people because they approach it with a preconceived notion. A sin that leads to death is a sin that has not been repented of. Repenting of a sin means that sin does not lead to death. Your father is unrepentant of his sins. Those sins will lead to eternal death. God tells us not to pray for someone who remains in his sins. We can pray that he finds his way out of sin and turn his life over to God, but while he stubbornly remains in his sins it would be improper to ask God to accept him or forgive him while he remains in his sins. To do so would be asking God to go against His own laws and His own nature. God does not sin nor accepts sin, so why should we pray that He overlook the sins of someone who doesn't want to yield to his Master?
No matter how bad your childhood was, you don't have to let it impact your life. All the choices you made are also your own -- the bad and the good. Just as your father has no right to blame his behavior on his mother, you cannot use your father as an excuse for your own behavior. Break the cycle of sin and start following God with your whole heart. Forget about the past and start living for the future.