In my opinion talent in measurement is the happiness you bring to people when you share that talent. The more happiness you bring to people the more talented you are. Like if you get a standing ovation if you're a singer, or if you get people laughing if you're a comedian, or if you dazzle people if you are a magician. That in my opinion is how talent is measured! :)

he is an overall 84, which is a terrible measurement of his talent in real life

If you have the talent for writing it should not pose a problem.

Water Talent, Tinker Talent, Animal Talent, Light Talent and Garden Talent I think that's all of them

The opposite of talent is non-talent