>>1282320The two screws are your limit screws that set the maximum range of motion of the derailleur. H limit determines how far outward, L inward. The other screw is your B-tension, which affects how close your upper pulley wheel gets to your cassette gears.
Did your housing seem grody at all? Might be good to replace it. Also maybe get some spray lube inside the shifter itself. Sometimes they have open spaces where you can get one of those straws in to really flush it out. Since you said you had a little plastic screw thing to get the cable out, you probably have one with two little screws holding the top cover on. Take that off then lube the internals.
