Hello jrat! Oh there is a lot of hope for your plant! Not too dire at all! The trunk looks firm and it is growing leaves, even though smaller right now. Give it time, it will bounce back. It is a slow grower, so just have to be patient with it.
Jade plants will store water in its leaves and trunk, it is a very succulent plant. So it wants to be watered thoroughly once and leave it alone to dry out. You have repotted it and have seen how shallow the root mass is, so it does not like being too soaking wet at root level.
The only fungicide I ever use for this plant, if I even have to use one is cinnnamon. Nothing else. I don't even give fertilizers to mine and it thrives very well. But as I have said earlier, my growing area/conditions are different. Your plant has just been in some stress of repotting and is trying to get through with the diminished light of winter, allow it to recover, give it time. You can add auxilliary light overhead too.
The cuttings you take when you trim the plant, you can also allow to form roots. Just lay it aside, and it should form roots too. More plants! A good backup!
Typically, I like to do trimmings when it is Spring. There is more vigor for the plants.
