***** NOT A TEACHER *****
I think that you are correct about the first "character."
So I think that "in character" refers to Mr. Jobs maintaining the "myth" or "expected role" of the first "character."
In other words, "in character" = living up to what we expect of him (in this case, his choice of clothing).
I am an old man. When I was young, nurses looked like nurses. They wore white uniforms. Today in the the United
States, many (almost all?) nurses do not dress in character. They wear (almost) anything they want. When I was
young, nuns looked like nuns (black habits). Doctors looked like doctors (white laboratory coats). Teachers looked
like teachers (suits and neckties, if you please). Ah! the good old days!