Your son is very much like my son was and still is at 37 years old.
I noticed my son was work shy after uni and he loved to party. We made the mistake of financing him for many years as he was trying to establish himself in a very competitive industry. He did work sometimes. Casual jobs that he either got fired from or walked out of. Once he did a sales job for 4 months before walking out.
He always had us to fall back on and that's the biggest mistake we made. It's only recently I stopped being the private banker and he's now living with his father, who hopefully has also stopped being the private banker. Our son is planning to return overseas in a couple of weeks.... to a place where weed is legal and micro breweries are abundant. The only difference is that I won't be paying for it any longer. I'm worried sick about him returning but I won't try and stop him. I've let go. You must let your son go too.
I realised my son was neither motivated or determined enough to establish himself in his chosen field, despite being extremely gifted. It's sad to see how he's wasted such golden opportunities. However, facts are facts. He put his love of weed and alcohol before anything else in his life. The result is a bleak and lonely future.... short term casual jobs, short term girlfriends who always end the relationship. Why choose to lead such a precarious life? Because he's an alcoholic and dope addict. All of his anxieties stem from that.
Like the others have strongly advised, step back and let your son live his life without any codependent interference from you. Let him go and let him fail. It's the kindest thing you can do for him long term.
It's very painful, especially if he's your only child as my adult son is but you have to stay strong and let him go. There's no other way. The years pass quickly and if you don't let go now, your son will be approaching 40 and his addictions will have progressed and his life a bigger mess than it is now.
Seek help for yourself and your own recovery from your love addiction.