If your idle mixture screw is all the way in and its still idling, that points to a major issue and likely the cause of all your problems. You need to check everywhere for vacuum leaks. Intake manifold to head, carb to intake and ALL vacuum lines. Something is leaking somewhere.
1990 YJ Islander, 4.2L MC2100 DUI HEI, 2.5" RE lift, 31x10.50 DuraTracs, HandenFab rear bumper / swing-out, Tough Terrain off-road camp trailer.