Actually, it is a pearl pied cockatiel, no lutino. The pied makes it impossible to tell gender by the most common way of looking at how clear the face is, but your biggest hint is in the fact that you say he is losing some pearl. I would guess you age estimate is off; can you tell me why you think he is two years old? If you had before and after pics of the molt, that would be extremely helpful. Male pearl cockatiels usually lose their pearling at about a year old. Some retain enough to still look pearled, but the amount I'm seeing on him would be extremely uncharacteristic for a two year old male. Others lose their pearls so completely that they appear normal. At the same time, losing any pearls would be odd for a female. My guess is that you have a male who is closer to one year than two. It should be much more clear when he finishes molting.
As for stance and whistling/talking, those can be indicators, but they are not reliable. I have a female tile who whistles up a storm, and I have had nearly silent males.
It's interesting to me that you say he doesn't know how to hiss. Baby cockatiels start to hiss at disturbances before they even open their eyes. They hear the parents doing it every time the box is opened, which means many will hear this behavior even from inside the egg in the last few days before they hatch, when parents and chicks are in communication. If indeed he didn't know how, then chances are very high that he was hand raised without clutch mates from an extremely young age, and possibly even hatched in an incubator.
Can you tell us any more of his story?