I think it's unfortunate that some folks dismiss ginseng or grafted ficus as the crash test dummies of bonsai. I've seen some really impressive trees that have grown from humble beginnings. As I have ranted elsewhere, most of them get killed off not because of anything done while learning about bonsai, but because of what's not done--not getting them out of the gummy soil at the beginning.
Based on my limited experience, some observations for Hannah:
Most species of ficus can have their leaf size selectively reduced without a large scale defoliation. If you cut across the leaf leaving a triangle of leaf and its stem attached, the leaf that grows out in its place will typically be about half the size of its predecessor.
By pinching off terminal buds, you can stop a stem from growing longer, while simultaneously freeing the axillary buds to create new stems. The leaves that are on that stem will not grow any larger from that point forward.
The biggest single contributor to preventing big leaves is lots of bright light. Selectively thinning the top of the canopy to let sunlight into the interior will help keep the interior leaves from getting too big.
And finally, ficuses, microcarpa especially, can drop leaves big time in response to an environmental change. Apparently they interpret it as nuclear winter or something, but it's enough to scare the daylights out of you and make you think you've killed it off. Not necessarily so---continue TLC and be patient, and they usually come back.
And for whatever my opinion is worth, I think it's a good looking little tree with some potential. Best of luck with it.