This great guy has no reason to fight the fight. He has you and mom taking care of business. That's OK, if it's OK with you.
There is an older but active thread on this forum " My husband died".
No doubt, this woman's husband started out, just like your guy did. Addiction is progressive. The outcome is either prison or death.
You did not cause this. You cannot control this. And you most certainly cannot cure this. What you can do is decide if you want to live this way, knowing, really knowing, that crack will never accept 2nd place. That place is reserved for you.