if you say that if you adjust it too much it wants to take off, then you are adjusting to the wrong end. You don't want to increase you idle, you want to lower it. If you lower it, I can't see it wanting to take off. Maybe I am not understanding you? Your idle speed affects you clutch and then the drivetrain, the brakes are on the drivetrain. So you solve the problem by first removing power from the drivetrain, by lowering the idle and reducing the clutch engagement.