Ive got something similar with my sister, and even falling down the stairs after a “couple” of drinks on a sunday night and breaking her neck and back (plus 8 other bones) hasn’t stopped her drinking
She has cut down a bit as fair as i can tell, but dispite going to AA meetings, her answer was “they don’t think i have a problem”
When she had her accident, she wasn’t sober until midday the next day, and if the accident didn’t happen, she would have been driving her son and friends to school that morning.
My only suggestion on the matter, is can he come and stay with you for a bit and break the cycle? Maybe discuss with him getting some hobbies out there, to occupy the day, so drinking becomes less of a hobby?