Since this has been in the ground for a few years, presumably with no root work, you likely have several years of work to do on the roots. If this were my tree I would dig it up, remove all roots facing down and non-laterally from the lowest plane of the root base, put in on a board, and stick it in an Anderson deep propagation flat, or similar. At the same time I'd cut back the lateral branches to a few buds. I'd then keep it out of freezing conditions and out of drying winds or afternoon sun until you see decent extensions on new growth. Don't let it dry out. Luckly, DRs are tough and can take aggressive root work.
If you don't focus on the roots now you're going to have a much longer struggle to get a good nebari. Likewise, it's not as important to focus on the top right now, other than apex taper and maybe initial movement in a few lower branches. Most branches will get too thick if you keep them now. You'll probably have to replace them later to reduce their girth.
Here's an example:
2021. Cut off the tap root, arranged remaining lateral roots on a board. Notice how few roots there are. I probably removed 90% of the roots during this potting.
2022. Removing crossing roots and pruning larger ones. Removing roots originating too high on the trunk.
2023. Continuing to work on the roots. And pruning back the top.
2024: Probably time to go into a smaller pot, and start focusing on the top.
