Re: Fan filters
for the first question: as you properly have guessed, you don't need a filter for the exhaust fan.
second: i am not sure about that question. i would think it will decrees the airflow a little, but it will catch more dust then example this one
third: the screw you use to mount the fan is the same screw that holds the filter.
so just mount it all at the same time by holding the filter and fan together while you screw it all in place.
forth: i have seen some filters come without screws, but the screws you got with the fan should work just fine.
MOBO: Asus Maximus 6 Hero - GPU: Gigabyte GTX 980ti xtreme - CPU: I7-4770K - PSU: Corsair AX760
RAM: Corsair Vantage 2x4GB - SSD: Samsung 840 Evo 512GB - Case: NZXT H440