Should I write the letter to my dad?

My mother and father divorced when I was an adult. They have both since remarried, my father married a woman who is younger than my youngest sister and they have a 3 yr old child together. He is 63, she is 31. I had a problem with his wife (she was talking about my children to other family members in a negative way) and I told my father about this, and I also sent her a message telling her. It has been 6 months since I have talked to him, but recently when I have called him he is not accepting my phone calls nor is he responding to messages I have left him. I am considering writing him a letter telling him how I feel about this and how self righteous it is of him to not respond to me after I suffered sexual molestation at his hands when I was 11 or 12 years old and I forgave him for that. We have never spoke of it and I assume he thinks I have forgotten. Should I write that letter?