But this loss you speak of is the issue. You would be better off to accept that he is not frum 24/7. And focus on the good side of him. I have that with my son as well. While he is not otd, he doesnt’ have a cheshek to daven very often but otoh he has a learning seder with a former Rebbe. And he is very honest and upbeat personality. Does not put on Tefillin daily. But I don’t love him less or am anguished about the lack of Cheshek.
It’s not exactly the same but I had at first disappointment in him, now not at all. I am proud of the good that he does at his young age and his good nature.
We are trying to suggest that you try to adjust your view in some way like that.
Also the cannabis, a long term study was just published that showed conclusively that those who used cannabis at a teen age and stopped in 20’s had IQ reduction against the same age group which did not use cannabis as teans but did in adulthood. you may want to print this study so he see this information.