You have some significant challenges with this tree, which with time and effort you can overcome. The first one that jumps out is the coiled, very thick roots. This problem won't get better on its own. Next spring just before budburst I'd suggest chopping them back hard while maintaining the flaring base. Dust the cut ends with rooting powder. They should grow new roots with no problem, and you will have solved the first problem. Your second problem is lack of taper, as others have noted. The general rule of thumb when working with cut-down nursery stock or collected trees is that the diameter at the trunk chop should be no more than one-half the diameter of the basal trunk diameter (this is measured above the root crown, or where the flaring roots join the trunk), at a point anywhere from about 10" to 24" above the soil depending on the basal thickness (most of my collected BC are chopped at around 24" in height, with trunks ranging from 3-6" thick). You can build taper in this tree, but you'll have to cut it back even harder than you already have. Judging by the first photo you posted, I'm guessing about 8" above the root base. Then you let a new leader grow wild until it gets almost as thick as the trunk below it, then chop again and repeat the process. This will take years, but will give a much better result.
Good luck with your project!
Zach
It's the "Art of bonsai" that I am new to. not Horticulture.
