Is it obligatory to fulfill the vow of giving a specific amount of charity "every month" from the husband's money, which has not been fulfilled for three years, and can it be fulfilled now from the vower's own money, knowing that it is not possible to make up for the past years?

Your vow is not binding, and nothing is required of you concerning it, due to the saying of the Prophet, peace and blessings be upon him: "There is no vow upon the son of Adam concerning what he does not possess." Thus, a vow concerning what one does not possess is invalid, and nothing is required by it.