McGay saidThis is a way for your superego or id (i confuse them) to pursue it's heart's desire, which really is for your mother. Your step-dad is a symbol of your desire to bed your mom.
No, I think you have your Odepious complex wrong, especially if he is gay. You have to remember that Freud based his Psychoanalytical theory on his interpretations, and on what he belived was normal. So, his Odepious complex and Electra Complex theories were made unintentionally specifically for straight people. And no, the idea that you were molested as a child is very unlikely, as repression of memories has been shown to be more unlikely than not, so if he did, you'd probably remember it. Maybe you just think your stepdad looks good. I used to think about my step dad like that after one time I walked in on him naked. It's nothing to be ashamed of, and will eventually go away. Unless you do have a relationship, and if you do, that's fine too.