After all that attention, the poor thing is having a nervous breakdown. Ficuses are sensitive to change. Just let it relax and don't fuss any more.
http://www.plant-care.com/planttips/1999/090399.htm
The Ficus is a very versatile plant as far as light goes. In the full sun it will have a thick canopy of leaves. But, in the dense forest it will grow very open with fewer leaves and thin weeping branches. This explains some of the leaf loss going from a higher light level to a lower light level. This is why every time you move that ficus from one room to another or turn it around you lose leaves.
THERE'S MORE
Just as birds migrate south for the winter season, the benjamina comes from an area that has very distinct seasons. The exception is that the seasons are wet and dry.
How does a benjamina prepare for the dry season?
It sheds its leaves. It reduces the amount of leaves to survive because it will not have enough water to support them during the dry season. When the rains return, new growth comes out and the canopy returns.
This explains another reason for leave drop. Moving from a grower to nursery and nursery to home, the plant is experiencing both light change and moisture changes. Is it the wet or dry season?
The survival mechanism for benjamina is leaf drop. It doesn't like changes, it is a creature of habit. Once you have decided where you are going to place your ficus (the more light the better), give it the same lighting, same amount of water and stay on the same schedule.
In case I didn't mention it, if you throw on some fertilizer you can also expect some leave drop.
Highly chlorinated water can cause leaves to drop.