If you take a look at the fine print just below the first section, it will give the definition of what the status implies. If he was nominated but did not recieve direct word for the nominators, it would still show up on the online app. page. It will be under "nomination status".
As for what the status of candidate "Should USAFA deem you competitive and/or you receive a nomination, you will become a "Candidate." Note that you may recieve a nomination and still not be deemed competitive by USAFA." So if your son has not recieved a nomination, it shows that he has a good chance to be offered an appointment (although if it doesn't say there is a nomination, I'm not sure what that would mean in the terms of an appointment). However, if it is candidate and there is a nomination, don't worry too much yet. The mass mailings still need to go out so there is still time.