Is the husband's action considered unlawful (haram) if he exchanges remaining medications from his private company insurance for other medications from an external pharmacy, knowing that he has sufficient money to purchase the medicine?

If the husband's insurance is commercial and not cooperative, then it is forbidden due to the presence of gharar (excessive uncertainty) and maysir (gambling), and it is not permissible to enter into it unless compelled. He is not entitled to any amount from the insurance sum except for the amount of premiums he paid. If the medications provided are within the amount paid, then they are his property. If their value exceeds what he paid, then he must donate the excess to the poor and needy, and neither he nor his family should benefit from it unless they themselves are poor.