hard to tell height???... dog ....

just cut back to live growth ...ken

Looks like mechanical damage. Trim as needed.

Hard to say.

Trim back to where the dead stops, or the first point where live branches are. when you have the dead twigs on your hand, i'd scrap the bark and cut a few one or two inch long sections. tou'd be looking for signs of canker, an area of sunken bark on the stem, or borer, little holes that would look not unlike small drill holes.

Odds are, you won't find anything. it just happened, and sometimes, the's things are inexplicable.

If it were mine I'd look at hopefully regionally targeted guides to bugs and blights affecting spruces. Or clip off the damage and take it to a nearby Extension Service office (open during banker's hours).