People do say 'what is he', and it doesn't sound wrong to a native speaker providing it is within context. If you are asked 'what are you?' without any context then the response would be one of confusion and maybe a person? a human? Having said that- just because people say it, doesn't make it right. It is a very lazy way of speaking English, and would never be used in formal situations. You should be asking, what job do you have? / what is your job? or most commonly 'what do you do for a living? '.

Yes, we can. When we want to ask someone's occupation, we can use this kind of what question,like "What are you?" or "What is he?".

The What asks about some Metadata, the Who asks about the essence

Think of A.'What is he to you' - it asks what is the connection between you; B He is my teacher But think of A.'Who is he?' asks about the name; B.'He is Malcolm X, my radical teacher'