"he's having hard time....
he is telling me that he has been dealing with it for his whole life (but he's just 30)...."
"in the end he decided to deal with it by himself." - And how's that ever worked out for him?
"Sometimes, I feel that he's playing with my sympathy."
Yes, he is. He's an addict, and that's what addicts do.
Your question:
"I wanna know how much is the chance of giving up cocaine & alcohol addiction without therapy treatment?"
Not a very good one, he's already tried that route.
Question you have to ask yourself is,
Do you wish to spend, let's say, the next 30 years on the ride while he "deals" with it himself?