Is it permissible to count the vowed amount, which I vowed to give if I committed the sin again, as part of the usual monthly charity? And is it sufficient to feed one needy person for each day I broke my fast in Ramadan and did not make it up before the next Ramadan began, and what is the amount of food that must be given?

You must avoid disobeying Allah Almighty. If a sin occurs, you must repent by feeling remorse and resolving not to return to it.

Regarding the disbursement of the vowed amount, if the sin has occurred, you have the choice between paying the amount or performing an expiation for an oath (kaffarat yameen). This is because it is a vow of obstinacy and anger, and its maker has a choice in it according to the majority of scholars.

If you wish to fulfill the vow and disburse the amount, it can be part of your monthly voluntary charity.

As for the second question: The sufficient amount for feeding is one mudd of food (approximately 750 grams according to the Shafi'is), or half a saa' of other than wheat (approximately one and a half kilograms of rice according to the Hanbalis), which is the most cautious approach.