EEPROM address definitions and delay
The first is a programming issue and the rest of your code will decide how you want to designate the sections of the device.

For the second, the datasheet gives a maximum of 5ms to program a byte or page, but you can use acknowledge polling to check if the device has completed the operation before that time has elapsed; see section 7.0, "Acknowledge Polling" of the Microchip 24AA256/24LC256/24FC256 datasheet for details.