Besides I had selected "All Coordinates" in CoordinateExtractor Transformer, only the first coordinate is extracted. How can I get all coordinates extracted?

The CoordinateExtractor transformer does extract all coordinates, but stores the values in a list. That list can be manipulated.

Two ways to store all coordinates in a comma separated attribute:

Use CoordinateExtractor followed by a ListConcatenator or

Use the CoordinateConcatenator transformer.

Hope this helps.