Clutch and gas pedal

Wade, unless I need more caffeine, the ABS light should not be related to your clutch.
The adjustable (if by adjustable you mean a multi-hook) quadrants are not really designed to tailor clutch pedal height so much as to dial in adjustment. MM sells a gizmo that does move the clutch pedal a hair; it's sole purpose is to adjust the height for better geometry.

Anyhow, On most multihook quads, one hook is a decoration (they are added to get around the patent on two hook quads). Chances are if you have a non-adjustable cable, you won't be able to use the other hook if you're dialed-in the first hook (there's normally not that much range of adjustment).

If the clutch is fully disengaging, the shudder should not be from the adjustment (a slipping clutch can cause glazing and hot spots, which = slippage/shuddering). If you installed an organic disk and there have not been a ton of miles put on it yet, they can shudder. I have a method of deglazing clutches but I wont post it. Otherwise, shuddering can be an imbalance issue, missing flywheel dowels, etc.

For the gas pedal: pop the hook and try to open the throttle by hand. I bet it sticks at first. The idle stop is probably turned in a hair too far (been there and done that).

Good luck bud.