it deffinetly does look like a benjima, based on that assumption and that you plan on doing this work in the summer when the tree is growing vigorously;
as far as the trunk chop is concerned, work it back like a pine, multiple chops over time.
chop each of the trunks to the lowest branch possible, and even though i'm sure you could, do not cut the terminal buds on those limbs just to ensure that limb will live. at this point you're not looking to use any of those limbs to develop into a new leader, you're just looking to reduce the height and keep the tree alive.
this should also cause your tree to backbud, and if it not, cut the terminal bud once you see new growth on that limb because you know the tree is still vigorous and wait. benjimina is known not to backbud, so you may or may not have success. worst comes to worst, there is grafting.
benjimina is not my favorite ficus to work with and I don't intend on owning any, but they do make great bonsai given the proper care.
the nebari can be developed very easily and the leaf shape and size is nice, just aware of the drawbacks of the species.