Is a wife's refusal to return to live in her husband's family home, where she witnessed incest, theft, and hashish use, considered disobedience to her Lord and her husband?

If the situation is as you described, then your refusal to live with your husband's family does not constitute disobedience to your Lord, and you are not obliged to obey him in this matter. Obedience is only in what is good and lawful, and living with your husband's family – if they are as you described – entails harm to your faith and worldly life. Your husband is obligated to provide you with a suitable dwelling where you can feel safe. We advise you to strive to reform your husband and encourage him to repent from forbidden relationships. If he repents and treats you with kindness, then otherwise, weigh the harm of divorce or khul’ against the harm of remaining with him, choose the lesser of the two harms, seek help from Allah, and supplicate frequently.