My reading of it is that the elevator will be more efficient in either direction for a particular deflection due to the greater leverage.
Yes, more effective due to the increased lever arm.
I see the consequence of the COG being out of limits as not being directly related to the efficiency due to leverage.
No, if the CoG is out of limits the elevator will not have sufficient authority (effectiveness due to amount of movement, surface area, airflow over it) to overcome the out of balance condition.
Indeed in spite of the greater efficiency there may still be insufficient elevator movement to counter the out of limits COG.
Yes, although it is unlikely to happen in practice in 'normal' flight, the theory is that the elevator, even with the effects of increased lever arm, would not be able to overcome the effects of a CoG that is out of limits.
The spinning example I mentioned above is one of the best practical demonstrations of the effects of a too rearward CoG. These issues have caused innumerable spinning accidents over the years.
This topic is valuable in that it highlights the importance of calculating the weight and balance of an aircraft.
There was the sad example of a PA28 a few years ago when two highly experienced pilots decided to spin the aircraft off the coast of Blackpool. The aircraft never recovered and both were killed - the CoG being outside of limits for
spinning that type of aircraft. Only two on board, no rear passengers but nevertheless outside the 'utility category' limits set out in the Pilot's Operating Handbook.
Although of academic interest only in this Thread, the practical consequences of paying scant regard to weight and balance can be serious.