Oof – so medication is totally off the table right now. As a temporary fix, can he download a biofeedback app that helps him measure his stress during the day to alert him to raising stress levels or is that going to lead to issues?
Also, and this is just a temp fix – can you encourage him to spend 10 minutes a day with no media, no phone, no nothing. There have been studies that a short daily meditation reduces stress. 10 minutes at the beginning or end of his day might help him.