Does one sin if he is unable to protect stolen money after clashing with the thieves, fearing for his life, and is he obliged to protect the money even unto death?

There is no sin upon you for surrendering the money to thieves under duress, and there is no liability upon you as a trustee, because a trustee is not liable for what is lost unless he has been negligent or derelict. The factory owner must pay the workers' wages, and you are not obligated to die defending the money.