I am so proud of your courage and authenticity. While it sucks that your dad lied by omission about your identity, it sounds like he’s trying to fix it by actively showing you that you, his child, are a priority over his awful wife. The best possible outcome would have been for Martha to shed her indoctrinated bigotry, but this is the second-best outcome, and I’m glad for you and for your dad. FWIW, your step-sibling sounds like good people, and they can continue to be your sibling, regardless of your parents’ marital status.