Welcome! Obviously we can't diagnose some one over the Internet, tho it's fun to speculate

I think your right! Your just seeing the tip of the iceberg. well put indeed. There is most definitely more to this picture and story! By what you mention it could be any thing or nothing. And don't limit it to just personality disorders. Could also be a mood disorder such as bipolar. You won't know for sure.

Is he moody? Does he go off in rage? Every violent? Criminal record? Reckless driver? Spends money like a drunk sailor? Disappears for days or weeks?

Even though we can not diagnose or say with any certainty what's going on. I would not discourage you from researching. Just keep in mind that often all these signs can be easily explained by drug abuse too! Could be a combination of both, then the doctor tries to figure out what came first. It's a long process.

Patience.