Prune off all other sprouts , just at the collar where they emerge. Remove addtional sprouts every 2-3 weeks as the plant recovers. And especially, prune out the poorer side of forks with included bark. Such forks are the main reason why trees and large shrubs split, often destroying themselves and damaging whatever they fall onto. Authors differ on the proper spelling.
Most authorities prefer crape, though some say crepe .
Probably a more important choice is whether to use two words, to hyphenate, or to run the words together. A crapemyrtle is not a myrtle, so its name should be hyphenated or run together.