He loves designing with Lego?. I also used to play with Plasticine, using my hands when I was in kindergarten. He is most probably an Extroverted sensation type. He seems to have An aptitude of music without training?, and An independent, want to try things by himself, Sensitive to others moods? He is identified as A feeler. My best guess is :He is probably an ISFP.
Yes artistic soul do have a talent of writing. No wonder He want to a be writer. Jung, a late psychiatrist whose theory referred by Isabel Briggs Myers who then extended it to the MBTI, also had an aptitude of art.
But Carl Jung type is INFJ.
You can check this.
His paintings.
Take a look at pages from The Red Book by Carl Jung | Books | The Guardian
His books.
Carl Jung publications - Wikipedia

But some notes, in story reading, that I like also read stories but, mostly comics. I do not read novels a lot. I also do not like to watch movies. I like to watch Only anime. One of the anime that I love to watch now is Russian Anime: Masha and the Bear. I also used to watch Naruto Shiphuden. I used to watch in my childhood : Sailor moon, nuku-nuku, Doraemon, Ronin Warrior, Samurai X. In comics reading, I used to read comics: Harlem beats, Kindaichi, Detective Conan, Astro Boy. I notice that it is extroverted intuitor type that is more enthusiastic in literature, like Novels, Poem, (with Fi). It is an Extroverted sensor type who can be an avid watcher of manga/japanese anime, cartoon, but do not read novels a lot. My sister (identififaction: ISTP) read comics, watch anime, and loves to draw, has some aptitude in martial arts:karate, but usually doesn't read novels for stories.