How do I stop auto-walk script (RenderStepped)?

I have it so that if you double tap LeftControl, your avatar will start moving forwards automatically. I want it so that if you press LeftControl again (bonus question: is there a better way to detect if the player pressed w, a, s, d rather than having to list "(inputObject.KeyCode == Enum.KeyCode.Button)" for each one?), RenderStepped will stop. This is what I have:

if (inputObject.KeyCode == Enum.KeyCode.LeftControl) then
		if IsEnabled then
			local now = tick()
			local difference = (now - lastTime)
			local Stepped

			if difference <= 0.5 then
				Stepped = RUN_SERVICE.RenderStepped:Connect(function()
							LOCAL_PLAYER.Character:WaitForChild("Humanoid"):Move(Vector3.new(0,0,-1), true)
				end)
			else
				if not Stepped == nil then 
					Stepped:Disconnect()
					print("disc")
				end
			end
			lastTime = tick()
		end
	end

When I press LeftControl to disconnect RS, it is unresponsive.