well you dont have to give up, and you can tell him that. and you can always be there for him, loving, and encouraging of the good and healthy decisions he makes- and you can tell him that. but you have a right to love him from across the country and talk to him on whatever terms you feel okay with. whether that is just an occassional letter, or not at all.
i had no contact with my brother, also an alcoholic, probably since i was 20 or so completely, after a chaotic episode where he threatened to kill me and rear ended my car. from 17- 20yo i attempted no contact.and before that- i WISH i attempted no contact.
they dont change until they change and sometimes thats just easiest. you can let him know you care and you love him but you have to live your own life and sometimes its healthiest with out others bringing you down.