Is it permissible to dispose of the remaining amount of the housing allowance, which is 2000 Riyals, knowing that the employer is responsible for providing housing regardless of the cost, and I have moved to less expensive housing?

The reference for these issues is the employee's contract with the employer and its regulations. If he is entitled to the fixed amount regardless of the housing cost, then there is no sin in benefiting from the surplus. However, if he is only entitled to the actual amount, then it is not permissible for him to take the surplus. He must consult the officials at the workplace to determine the extent of his entitlement.