It really depends on why he went off. Generally nowadays is an emotional reason not an intellectual one (although to justify it after the fact they may seek intellectual reasons as well.) important to know the cause. If it was due to negative emotional experiences, then probably number one is not advisable as it implies, atop the baggage he already has, that you don’t care about HIM, but just about his frumkeit level. Generally, the way to bring them back is with love and unconditional acceptance (although that doesn’t mean accepting / encouraging their behaviour, and also doesn’t mean you can’t set rules for their behaviour in your house).
But really every child is an individual, and healing the cause of why they went off helps to bring them back.
Also every mitzvah they do / are happy to do with you, counts. It’s not all or nothing.