Q2. Many people i fly with don't seem to use WING anti ice when passing icing conditions but only use ENG anti ice. Is there a bigger penalty on fuel or is there any other explanation ??
Wing ice accretes about the same way that windshield wiper ice does which is a visible sign that you are in icing conditions in-flight.
Engine ice can accrete behind the fan blades (due to low workload in the compressor) and is not visible. Furthermore the sucking of the air at low power conditions further depresses the temp in the front of the engine at low power conditions and results in the freezing point being reached before the outside air temperature at the windshield..
Now add to this the much greater concentration of water inside the engine again due its capture at low power and once you reach the freezing point it accretes faster than the visible windscreen.
In the case of icing, flight safety far outweighs fuel burn penalty and thus the FCOMS are written arround that concern.