How old is your stepson now? About 12? He's old enough for a heart to heart talk about your childhood, how you were molested and that made you fearful to be around children and to hug and be loving. Not because you would molest anyone but because you developed a fear that never went away. Tell him you have always loved him, and are truly sorry, and want to make up for lost time.
I think a lot of your marriage problems might be helped if you can gain some trust from your stepson. They can be put on the back burner for now. She may see what you are doing and love you for it.