This is the way I would write/say them:
1. At what station must I change car to go there?
"At what station do I need to change trains at, in order to get to Paris?"
"station" implies a train or subway, "car" refers to a single car as a part of the whole train. So if you changed only the car you were on you would be on the same train.
2. New York is larger than any other city in Korea.
"New York is larger than any city in Korea."
"other" implies that New York is in Korea.
3. He is not the merchant what his father wants him to be.
"He is not the merchant his father wants him to be."
4. I have a little doubt that he stole the money.
"I have little doubt that he stole the money."
5. Reading is the act of interpreted printed and witten words.
"Reading is the act of interpreting printed and written words."
6. Anything more was not said about the painting.
"Nothing more was said about the painting."
7. The number of illiterates has steadily declined.