Does driving with your foot always resting on the clutch (not pushing) generally wear it down?
It absolutely does. It's called riding the clutch. Even though you "believe" you just have your foot there, it forces the pedal down and takes up the slack which is there. This causes the throw out bearing to ride against the clutch fingers, which presses so ever slightly and causes the clutch to not have as much grip. This causes the clutch friction disk to slip which causes heat and ultimately wear. I've found in these situations, the clutch doesn't necessarily wear out, but the extra heat caused by the slippage causes heat cracks in the face of the flywheel. This causes the driver no length of pain in driving and it is a chore. In the process, the throw out bearing wears out very quickly as well.
Resting your foot on the pedal is a very bad practice.
I do not see how you can rest your foot on the pedal without exerting any force at all on that pedal. What is the point? You might as well use the pedal properly and ONLY apply force to it when required. Resting your foot on the clutch pedal WILL adversely affect the operation of the clutch release bearing (throw-out bearing as our American cousins call it) by generating friction and subsequently heat, which will absolutely wear out those components prematurely.In extreme cases, the friction plate will slip causing heat, loss of drive (clutch slip) and again, premature failure. Leave the pedal alone unless you are changing gear, simple!
For one thing, letting off the gas and, not pressing the clutch should help slow the car better, then hitting the brakes alone with the car in let's call it neutral. because the transmission will help slow the vehicle with the deceleration of the engine. As for "riding the clutch" keep your foot off of it yes it will wear out the moving parts in your transmission. also don't panic in a situation where you lock up the wheels.