Your plant is Acuba japonica. When did you transplant it? These plants prefer some shade in both winter and summer but I do not believe you have winter damage--at least I have never seen local specimens looking as bad after the worst of northeastern winters. Cut back to healthy tissue if you want to try to rescue it. These regenerate quite well if happy. I have had deer eaten one recuperate from the base and grow new plants at ground level. Wonder if some kind of blight is affecting you regionally.

If there is a green cambium layer under the bark, then it is still alive. It's chances of survival sound slim. Cutting off dead wood and planting in a shaded area in moist, well-drained, acidic soil would give it the best chance. Fertilizing at this point would just increase the shock. Then if and after it recovered, it would need to moved to a place with more light so that it would begin blooming. They need some sunlight to bloom.

Im a Phoenix gardener and can offer a few nuggets from my experience... did you use pre-packaged cactus soil? If so, I would suggest that this was not a good choice (sorry). I tried it once in a raised planter and would up digging everything out and removing the 'soil' and replacing it with something else. I found that it just could not hold water after it dried out and the plants were suffering. Since then, Ive mixed my own soil mixes and used my native soil as the base component. Ill mix in some 1/4" minus or pumice to get it draining better. I even have one raised planter that is pure 1/4" minus. After trying to grow and killing so many ice plants I cant even count, I gave up. They just burnt out in the summer no matter what I did. Not to say it can be done, I jut am not the one to do it. I think of them as annuals here. Ive killed some crassula too so Im not the best one to comment on those. Maybe looking into plants that have caustic sap or some other forms of natural protection from the bunnies would help (like euphorbia).

I am in central Illinois and don't water too much, I had this for maybe two or three years and then it dried up one year. It was in a shadier spot too, might have gotten overrun by napeta or euphorbia. I had noticed that it was creeping into the lawn greedily, but it is gone now and the euphorbia is moving in to take its place! I would water yours well, keep it in a mostly sunny area (but not where it's going to get it the harshest sun) and watch for new growth. Or you could split it in a few pieces, spread out the roots when you plant it, and water it in. Keep an eye on it cuz it can help itself to it's neighbors' territory!