You don't have to
"give up" on him. Pray for him, send positive, healing thoughts his way. Hope that he will see the light and begin a recovery plan in earnest. In that way, you don't give up on him.
It's very hard to stand by and watch someone self-destruct. I think the only way we can hang in with these people is to turn them over to God as we understand him.
Welcome to the forum cmac. You will find a lot of experience, strength and hope here.
Peace,
Gabe