It's very frustrating. Addicts who are using actively do not think like we do or they would stop. Addicts quit every day. Until/unless they do quit, they live in a world of no rules, no responsibility and selfishness.
I am sorry that your middle son is still in the depths of addiction. You are right about him being very sweet natured when sober. I wish I had a magic wand that would fix addiction. My brother is (and has been) lying about his sobriety for quite some time. My mother buys his lies about his sobriety. The rest of us don't. You don't have a truck full of beer cans if you are sober. Or a 12 pack of beer in your home. Esp when NONE of the family would drink around you in your home.
I hope that someday someone figures out a real way to help those with addiction. Until then, all we can do is support each other.