Hello,
Open device manager and uninstall the old driver listed as PS/2 mouse and restart laptop.
Download and install synaptics driver from asus G75VW win 8 64-bit
HERE (make sure you have synaptics touchpad and not the other one). Restart laptop. Assuming you already installed all other software, atk package, keyboard filter ...etc, your fn+F9 should now enable/disable touchpad. Not only that, your smart gesture should also work. Yehey.