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When plants have been damaged by a freeze, it is best to avoid pruning right away even if parts of the tree look dead. Pruning can allow further damage from cold weather to happen, and even if all the leaves fall off, the tree might survive and grow back next spring. The best course of action is to wait until spring to see if the leaves grow back. Then if there are dead portions of the tree, you can prune those away. Here is additional information that should help: https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm

You can prunie this thing up with a little knowledge on the subject. This article can help you: https://www.gardeningknowhow.com/ornamental/shrubs/bottlebrush/pruning-bottlebrush-plants.htm

Although it may look rough now, when you prune it up come early spring then it will come back just fine. If you are really concerned about the cold, you can cover them with burlap on the colder nights.

Here is an article for more information on the care of the plant: https://www.gardeningknowhow.com/ornamental/shrubs/bottlebrush/growing-bottlebrush-plants.htm

Yes. You are within the hardiness zone, and rarely in history have the temperatures exceeded the lowest zone temps. This will survive down to about 15 degrees with some damage. This article will give you more information on how to care for these: https://www.gardeningknowhow.com/ornamental/shrubs/bottlebrush/growing-bottlebrush-plants.htm

Your trees could potentially have a borer or a root rot disease. But, more likely, the problems are caused by environmental conditions. Check whether anything has changed recently in the trees' environment. They may also need fertilizer- bottle brush trees tend to develop iron deficiency.

Yes. This will help it quite a bit. Here is an article for more information: https://www.gardeningknowhow.com/ornamental/shrubs/bottlebrush/pruning-bottlebrush-plants.htm