I am so sorry for your pain, but you ARE most definitely doing the right thing, as hard as it is.
I believe his intentions are good. But they've been good before and he's gone right back on his promises after a few months. I know deep down I don't believe him when he says he'll never touch drugs again and I don't believe him when he says he wants to have a life without them. I wish I did! I WANT to believe him, but I can't.
This is how it is with addiction and it gets repeated over and over until we just know it isn't going to happen, no matter how sincerely said. They cannot promise themselves that they will never use again, let alone anyone else. It just drags you in to his hell and you can't drag him into sobriety, no matter how hard you try. If love could save an addict, not one of us would be here.
You are very wise to remove yourself entirely from the situation. Time and actions will tell you all you need to know. Words mean nothing at this point, no matter how sadly or sincerely delivered.
I am glad you have family to support you, emotionally as well as financially. They may seem harsh and unable to really "understand" but trust the clarity that they have, something you will find only in time and as you heal.
Stick around and know that you are not alone. This is a good place for support and to learn how it has been for others.
Hugs