What is the ruling of Islamic law regarding the husband and his family neglecting the questioner at social events, and regarding the debt they owe to the questioner's mother, and regarding the husband's family keeping the apartment key, and what should the questioner do about the material and moral problems she faces with them?

Your relationship with your in-laws regarding visits and gifts should take into account prevailing customs, as long as they do not violate Islamic law. A husband is not obligated to spend on his wife before consummation of the marriage unless the wife presents herself for consummation and the husband refuses, in which case he is obligated to provide for her. If the wife leaves her job based on her husband's promise to provide for her, it is commendable to fulfill the promise, and it becomes obligatory according to the Maliki school if it leads to a commitment. Debts owed to your mother must be repaid unless the debtors are in financial hardship, in which case they must be given respite. Your in-laws are not entitled to take or benefit from any of your household furniture without your permission.