I know this is a nofap group so forgive me, but for me the key is really cutting out the P. I have failed and failed again really quickly going the nofap route but have had some success in the past with no P and definitely limiting my MO but not being worried to cut it out completely. When the urges are so strong I just get the MO over with and I don't want to engage in the P anymore. Again, maybe this is the best way for him. Also, therapy or you and him or him really verbalizing why he keeps relapsing. what is he feeling that led to relapse, how did he become addicted. I find talking through my thoughts has been a big help as well. Best of luck to you both.