It's not as simple as can people, in general, change or can't they. Abusive people are narcissistic that cannot be changed.
Drug and alcohol addicts act like narcissist do, but therapists cannot be sure if it's the addiction or the personality disorder until person is clean for long enough to tell. In your husband's case it could be, you claim, it was drug abuse that made him abusive not narcissism.
So as long he is clean, he is safe to be around.(So, you say) Trouble with addiction is people relapse throughout their lives...
So, if he starts using again, he will become violent again....Even as far as alcoholics go,your husband was bad.Not all drug abusers show violent narcissism but they do display narcissistic behavior.
So your husband is still a piece of violent s.h.i.t that abuses physically weaker than himself, as in women or children, he just needs a few weeks drinking spree to start him off....
There could be no reason ever to go back to someone who was physically and emotionally abusive to you.
That was the first error in your logic, i wonder how trustworthy your report of you husband not being abusive is even...
In theory it is possible that he is now a changed man as he was only 16 and a heavy drug and alcohol abuser when he was abusive, but this is rare...
You know what's not rare, people being abused in a relationship where abuse is normalized to a point they go around telling everyone their abusive partner is not abusive anymore...
So really, it's not as simple as do people change...People do change, but not so much that they can go from personality disorder to mental health...
Even if you husband was of the rare men who were only abusive due to drug abuse and he is now safe and sane, you are setting a terrible example for young women or any women struggling to cut someone who got abusive on them from their life...
Instead of broadcasting you taking back a man who has hit you before as a success story you should STFU about it. It's nothing to be proud of...
Finally, adding into my reasoning the fact that your own friend sees he hasn't changed... Chances are you are being abused daily and your 2,5 kids as well...
Well done...Great job...