My husband is a recovering heroin addict. You cannot beg, plead, manipulate or love them sober. The only thing that works is professional help and the addict accepting that help.
I know you will try to convince him.. and feel that in someway things will be different between the two of you.. but addiction is progressive. That means it starts out not so bad.. and turns into your worst nightmare.
You can accept him the way that he is. Accept that without professional help - his disease - addiction - will get worse and their is not one thing you can do about it. Maybe - Maybe - you can convince him to get help.
However, when I was an addict - if anyone tried to separate me from my drugs or convince me I needed help - Well.... they would have been wrong. I needed to decide that for myself.