Is the amount of money spent by the father with the intention of zakat to save a young man from ruin considered acceptable zakat, knowing that most of it was spent in ways that displease God and only a small portion of it was used for the project?

Verse 60 of Surah At-Tawbah clarifies the categories for zakat distribution. A poor person is one who does not possess enough to meet their needs or is unable to earn a living, while a needy person (miskin) is in a less severe state of need. Each of them is given what suffices them. However, someone capable of earning but too lazy to work is not entitled to zakat, based on the Prophet Muhammad's (peace be upon him) saying: "Charity is not permissible for a rich person, nor for one who is strong and healthy," and his saying: "If you wish, I will give you [from it], but there is no share in it for a rich person, nor for one who is strong and able to earn." Therefore, if the young man mentioned in the question is capable of earning, can find work, but is hindered by laziness, he is not entitled to zakat. However, if he cannot find work, then there is no harm in giving him from zakat what enables him to work and earn. If your father gave him zakat and he was deserving of it, then his action is correct and fulfills his zakat obligation. The fact that the young man relapsed does not invalidate the zakat, and he should be followed up with and advised.