Of course it'll be rough if it's idling as slow as 450... Especially if that's an automatic, in gear. Probably not the fuel filter, because when it's idling is when it needs the least amount of fuel.

Tune-up!! Plugs, wires, cap, rotor, adjust spark timing, run a bottle of Techron or something like that. Check/clean your throttle body - is it all full of black crud? Then adjust your idle. Then tell us if it's still shaking.