Update: the tree started off a little slow this spring, but is taking off nicely now. This spring, I repotted into fresh bonsai soil, with no root pruning. It has been in full sun, with weekly fertilizing using Miracle-Gro at regular strength. No pruning or trimming has been done. There has been a lot of new growth budding from the crotches of green branches, but so far, no back budding on older wood. Some of the tips have extended, some not. I was really hoping for stronger back budding, especially on older wood. All new growth is juvenile, stronger on the top fork than the bottom one. I have removed all the wire and replaced with a couple of guy wires. The shape didn't completely hold, but I was worried that since the tree is weak, that the wire was compromising its health. There was a little cracking at the bend of the bottom fork, so I loosened up the guy wire and placed some putty over the crack.
Overall, I'm quite happy, though I did hope for more back budding. My plan is to let it keep running for the rest of the year, and contemplate some strategic pruning over the winter. No repot next year. I'll leave it potted as is for a couple of years. Next year I'm hoping to begin condensing the foliage a little.
Any further thoughts are appreciated.