pito:
..the sketch size is 6.5k. Does that mean I need a chip with a flash memory of 6.5k or less?
You mean the size of sketch source (the text you see in the IDE), or the compiled binary size?
From the source size you cannot judge on the flash memory required, as a 6.5k source code may create binary of any size..
I assumed it was compiled size as when you upload or verify code in the IDE the console window says at the end how large the code is out of a maximum of 32k (the UNO's flash size).