Hi Scott,
If it were mine, I'd check the roots to see if it needs repotting. If it can stand another season in this mix, I would simply scrape the top of the soil and add some good mix (it looks like it's got Akadama, which is good)
Then I'd just concentrate on the upper part. Repotting, air-layering and the like can wait.
The main problem I see here is what I circled in red.
First, it's got several cuts that form a bulge, secondly, I think that you will have to choose between one of the two branches and I'd cut the bigger one. The movement would look better IMO, and it will help with overall "conicity".
If branch nr. 2 is on the trunk, or very close to it, I'd keep it.
The more you cut on a J. maple, the more likely it will bud out below, like in nr. 3, or even 4 : if that's the case, I would let the new shoots grow freely.
Nr. 5 would be the new leader. The longer it grows, the better for the future of the tree, you can prune it later.
The first branch on the right has also marks of pruning that are not so "elegant" for the moment, but it's the first branch and it's strong, and it's much better than having a first branch which is weaker than the second one.
After a year or two, maybe an air-layer whare the small twig can be seen on the right, or a little below.
View attachment 279060
PS: I much prefer using a grow-bow than planting a tree in the ground. The subject has already been discussed here, so I won't develop.
PPS: is that a beech (fagus) on the left?