|I purchased 3 of your|
|Endless Summer hydrangeas bloom on both old and new wood so even if your plant freezes down to ground level this winter, the new shoots it develops will produce flowers next summer. I'd leave the shrub alone for now. Next spring, just as the buds begin to swell, you can prune it back to about knee-high. If the stems do not produce new buds but you see new growth coming from the crown of the plant, prune off the winter damaged stems to make room for the healthy new stems.
The holes in the leaves are probably caused by insect feeding; the brown spots are simply the leaves' way of sealing off the damage. All the leaves will drop after the first hard frost. At that time rake them up and remove them from the garden. Healthy new leaves will arrive in spring.
Enjoy your new hydrangeas!