But, what i want to know...is can they change?
Sure. The question is are they willing to do the hard work over a long period of time so that they can change. A lot of addicts can talk the talk. The question is can they walk the walk.
You say the love you have for him is "indescribable". What about the love and respect you have for yourself? Do you really want to hitch your wagon to someone that has completely and utterly self destructed the way he has? Do you want to risk your well being for someone whose track record is abysmal?
Just because we love someone doesn't mean we should be with them.
And if he's truly serious about recovery and serious about turning his life around, then he'll recognize that he's unable to be a fully committed partner in a romantic relationship at this moment in time.
If you really love him the way you say you do, then allow him the space to work on him.
Best,
ZoSo