Is it permissible for a father who lent money subject to zakat to his son to take the value of the zakat to distribute it as he sees fit, or to compel his son to distribute it, or is it not permissible for the son to pay the debt from zakat money?

The zakat on the money is obligatory upon you, as you are its owner, unless your son volunteers to pay it on your behalf. If your son is well-off and not procrastinating, then you must pay zakat on the money every year. However, if he is in straitened circumstances or procrastinating, then you must pay zakat on it for one year when you receive it. The basic principle regarding zakat is that it should be given in kind, not in value, unless the kind is not available and the value is more beneficial to the poor.