Is what the husband does, selling curtain fabric at a much higher price than he bought it, and increasing the fabric meters for customers, considered a sin upon him or upon the shop owner? And is continuing the marriage to him considered unlawful?

A merchant's significant profits, without deception or fraud, are permissible. However, an employee's act of increasing measurements fraudulently is forbidden and constitutes unjustly consuming people's wealth. If the shop owner is aware of this, he becomes an accomplice in the sin. This matter does not affect the marriage. The wife should advise her husband to abandon fraud, and if that leads to him leaving his job, then he must seek another. If the fraud occurred without the shop owner's knowledge, the employee must return the rights to their owners or donate their value as charity. If it was with the shop owner's knowledge, then both are accountable. The wages the employee receives for his work are permissible for him because the contract was made for permissible work.