Is it permissible for a father to marry off his son using Zakat funds, knowing that the son is financially struggling, uneducated, and earns a low wage?

If the father is able to marry off his son, then it is obligatory upon him, as it is part of the essential maintenance. It is not permissible for him to marry off his son using money from his zakat, unless he is unable to marry him off. In that case, it is permissible for him to give his son from the zakat according to his needs, without extravagance.