a) Is it realistic that Superman wears the letter (S) on his chest? If this letter is from his home planet, where would his father have known that people will call him Superman? If it were the initial of his name, it would be understandable. Which alien would make a (S) on his chest, so he is called Superman?
The S on his home planet means Hope. It was Lois who thought of the name based on that S and named him Superman.
b) A pair of glasses as a perfect disguise? Isn´t it strange that when Superman wears normal clothes and has a pair of glasses on his nose no one recognizes him? Well, his hair is a little different, but does it matter so much? What about his face, his voice and his body size?
The reason why he wears glasses is to hide his unique blue coloured eyes. A lot of people don't know Superman has another side to him, they believe he is constantly helping around the world. Plus other people have dressed up as Superman, I.E Martian Manhunter who can change his appearance to be like Superman and they both have appeared in the same place. So people just don't realise it nor think of a god-like being who would do this. Like Lex. Lex found out and wouldn't believe it.
Recently in Batman comics
Joker found out that Bruce was Batman but rejected it. He doesn't want it that way so refused to accept it