Your low limit is set on the same temp as the high limit. The low limit should be lowered to 110* which makes it 20* lower than the high limit. Yes it would save you more oil by giving the burner a chance to rest while the temp drops by 20* rather than short cycling.
The brass needle points to the setting you desire while the aluminum needle is the limit to what the brass one can be set. I think you will find that the aluminum needle can't be moved, but rather is the manufacturer's safety stop.