That is a really big Jade! The message its trying to send is there aren't enough roots to support the top. Its sacrificing old leaves and branches to support new growth. The first thing you need to do to rescue it is find it a sunny sunny window and maybe even add grow lights. Without sun it can't photosynthesize so can't use moisture in the soil or support new growth. What kind of soil is it in? That's a big deep pot so the soil may be staying too wet too long. That will cause roots to rot and even more branch drop. How do you determine when to water? In winter with low light, water consumption will be minimal.
Its time to develop a backup plan. Instead of tossing green aborted parts, plant them.
