[JasonCSU]

If the clutch were slipping, I would think it would still transfer some power through the transmission and then to the wheels. You should certainly smell a slipping/burning clutch as well. The odd thing you mention is how the revs don't seem to match the amount of throttle you apply. With the transmission in neutral, how does the engine respond when blipping the throttle with no load on it? If the clutch were toast and not transferring any power, I would think the engine should still rev normally.