Well thanks, cotton ball. I suppose we all skin animals in our backyards & make everyone's lives a living hell because we have nothing better to do?

Little voice, "Do you think he is a sociopath?"
Some of the people who have the strongest emotions are the ones who try harder to suppress them... Your boyfriend has probably had some kind of trauma in his childhood or later on that causes him to disconnect. He doesn't appear to be sociopathic, from what I can tell. They usually have a little bit more going on than just emotional disconnect or depression.

"Is it really true that he will never change?"
If he has a personality disorder of any kind, it's highly likely, but there are ways of dealing with it.

"Will he never be able to settle down with someone?"
That's a mixed bag. Some of us are more impulsive than others, more malicious than others, less content than others... My impulsivity wavers, I'm not really that malicious unless provoked, & I tend to waver in contentment. All of those factors, along with finding the right person, contribute to the ability to settle down. I'm doing fairly well at being a good girlfriend, but it's a co-dependent deal in some ways, so I guess it's still kind of self serving.

"Are people ever happy that are this way?"
It depends on the severity. But usually if someone can get their own way, happiness is achieved!

"Should I continue to stick by him?"
Maybe, maybe not. It seems like he treats you well enough & feels kind of helpless about the whole situation... It's highly unlikely that he has anyone else to discuss these things with. You may as well continue to support him as long as it doesn't negatively impact you. But if it comes down to your happiness VS his? Go your own way. He'll find his.