I've had a lot of experience with Korean boxwoods, but not so much with other types like yours, and don't know the ins and outs of their care in your climate, but I'll tell you what I think are some general hints, and you can take them with a grain of salt.
They are a fairly robust tree. It may vary among different varieties and climates, but they seem to put out more roots more quickly than almost any tree I know, and I've had no problems at all with root pruning and such work at any time of year. BUT, YMMV!
The wood is a real pleasure to carve, and it is considered to be be one of the few deciduous trees that resist rot well enough to be advised for jins and such even by the strictest of traditionalists. Keep that in mind as you chop it back. A major chop done flush with concave cutters will take many years to heal - you might as well either leave a bit to make a jin, or hollow out the scar as a deadwood feature.
When you chop it back, many varieties will not back bud on a branch if you don't leave at least some foliage, so don't chop below that if you want to be sure you don't lose that branch.
People say they are too brittle to wire or bend, or that the wire will easily dislodge the bark without extreme care and such, but that has never been my experience. Once again, though, YMMV.
Here, we never get pests and such, at least on Korean boxes, so I can't advise much in that department.
Hope that helps.