Drug Addict - only when he had no case to follow and his mind was restless. Cocaine stimulates the mind and works in a different way to alcohol.
Sociopath - no for the reasons you said. Yes he did care about Watson and about his clients. He had a deep sense of moral justice.
Would he have thought enough about himself to attritube a label onto his character? No. He didn't seem to care much when Watson rebuked him for his coldness.
Would he have been confused about why people didn't get him? No, he actually showed great affinity with people when the fancy took him. He had a great understanding of people which is why he was able to read them so well, not just from their clothes but from their expressions and what they said as well as failed to say.
I think we will have to agree to disagree.
That Gatiss and Moffat have a great fondness and knowledge of the character is clear enough and for that they demand respect. But everyone reads things differently and I think they have changed his fundamental character.
They brought in parents, a traumatic childhood, a competitive brother, etc. They sought to explain when I feel they could have left all that out and it would have made it much better. It does nothing to add to the stories, knowing about his childhood and background. It's just something they like to do, it's their mark.