There's a lot going on in what you describe so far as family dynamics. Can you say if mom or dad were substance abusers themselves? Decline if that's to much to ask.
I know what you mean about childhoods. You might be what is called a
resilient child. I'd be willing to bet that you are. I am one, too.
If the person isn't already in therapy I would really, really, recommend that because there is a LOT to unpack in those relationships. How he was raised and what the environment was like isn't his fault. He didn't create it. He simply grew up in it and adapted to it.
Still...there's a good guy under all that, right? He's not a grade-A tosser. I absolutely believe he's a good guy. I know you well enough and you have had a depth of insight from the beginning of our knowing each other and at an age I wouldn't have ever expected you to. No one on that board expected it!
So...the book I was going to recommend was written for ACOA's (adult children of alcoholics). It shows the results of alcohol abuse in the family and how it creates certain dynamics and certain roles of the family members. I am positively certain it applies to drug abuse in a family as well. No question about it although I don't recall it covering things like how drug abusers resort to stealing even things from their own family out of desperation and the need to use.
What else was I going to say?
Oh yes. If you want, I can teach you some behavior guidance techniques we use for young children. Why? Because pro tip: they work for adults, too.
And they might take the strain off your reactions because you'll already know what you're going to say and do to handle a situation...with practice.
Here's a link to the book and I think there's a new version of it. Check out the summary and if you think it sounds useful, heck, I'd go to eBay to pick up an inexpensive copy. These are US Amazon links:
https://www.amazon.com/Will-Never-Happe ... 0345345940
Oh look! The new version has changed to include addiction!!!!! Check THIS one!!! If it sounds good to you...THAT'S the one I would get!!
https://www.amazon.com/Will-Never-Happe ... b_title_bk
Claudia Black's bestselling classic on the experience and legacy of being raised in an addictive household.
In an all too familiar scenario, played out in millions of homes every day, children who grow up in addictive families abide by certain rules: don't talk, don't trust, don't feel. The rigid survival roles and youthful coping behaviors they take on, such as the responsible child, the adjuster, the placater, and the acting-out child can eventually contribute to problems of depression, loneliness, and addiction in adulthood.
Using poignant personal stories, thoughtful explanations, and helpful exercises, Black helps readers gain personal insights and develop new skills that lead to a healthier, happier, more fulfilling life.
While continuing to recognize alcohol as the primary addiction within families, this newly revised edition of It Will Never Happen to Me, which has sold more than two million copies, broadens concepts to include addictive disorders involving other drugs, money, food, sex, and work.
p.s. If you want me to do a guidance thing chose one situation and describe it (like you are a camera filming it--show it to me) including what the conflict was about and what each person said. I'll give you a little demo.
ETA: I do have private messages here.