It sounds like he needs professional detox. I don't mean to be harsh, but you are not qualified to deal with this, most people aren't.
I'm both a recovering addict and a codependent who has/had loved ones still using. I was also a nurse before I lost that career to addiction. FWIW, money is not always an issue when we want to use. There are other ways around that, none of them good and they could affect you.
I pray that he seeks professional help and you allow it. Had the people who loved me not allowed me to hit bottom and dig myself out of the hole I'd dug myself into, I'd not be in recovery right now.
All said with love and compassion. I've been where you are, and I will never do it again.
Hugs and prayers,
Amy
He is shooting up methadone? This is not safe.
I can sense how much you love him, but you can't fix him.