Is it permissible for an accountant to take his financial dues himself if the manager wrongs him and refuses to give them to him, knowing that the previous accountant did so and was punished?

If your current job involves assisting with bribes or interest, and you cannot avoid it, then you must leave it. However, if leaving it would cause you significant harm and you find no other alternative, then you may remain until you find another job.

Regarding overtime work: If it is based on a contract or common practice, then you are entitled to payment for it, and the employer must pay it. If the employer denies your right, you may take it by stratagem, provided that you do not betray trust or take more than your due. However, if the overtime work is voluntary and not based on a contract or common practice, then you are not entitled to payment for it.